1. If you have a Windows computer, you must obtain and install all of the following: a reputable antivirus program, a software firewall, a junk-mail filter and an antispyware program. Even if you own a Macintosh (Macs have been unaffected by most of these threats to date), you will still need to turn on your computer’s firewall and employ a junk-mail filter.

2. Upgrade to the latest versions of the leading Windows web browsers, Microsoft’s Internet Explorer 7 and Mozilla’s Firefox 2.0, both of which warn you when a web page you’re visiting appears to be phony. (The new Internet Explorer also has under-the-hood security improvements that close some of the holes plaguing older versions.) You might also consider add-on software, like McAfee’s SiteAdvisor or the new Norton Confidential, which warn about fraudulent sites and, in the case of Norton, also about malicious software on your PC. On a Mac, consider using Firefox 2.0 instead of Apple’s Safari, which, while very good and generally secure, lacks a fake-web-site detector.

3. Never respond to or click a link within any unsolicited email message from a financial institution — even your own — no matter how official it looks. Crooks have become skilled at mimicking logos and typefaces used by banks, brokers and payment services like PayPal. When you click on links within these fake emails, you’ll be taken to web pages that look like the companies’ official sites, even down to the address, but they’ll steal your log-in information. Be especially wary of email from a financial institution that asks for account information or says you must log in at a linked site to address a problem. You can phone the company to see if there really is an issue. Obviously, this caution doesn’t apply to some financial emails, such as confirmations of online stock trades you’ve just executed. But in general, you shouldn’t conduct financial transactions via email or links in email. Instead, go directly to the financial sites you use.

4. Similarly, never act on emails offering stock tips, miracle pills or the chance to earn money by storing millions from overseas in your bank account. Sounds obvious, but in the past these scams might have cost you a little money. Now they may be part of more-damaging identity-theft schemes. Treat such come-ons the way you’d treat a stranger in a bad neighborhood who made such promises.

5. Never, ever download software from a company or web site whose honesty or veracity you’re not sure of. If a site says you’ll need special software to use its features, don’t bite. Even if the software is well known and safe — like RealNetworks’ RealPlayer, Apple’s QuickTime or Adobe Flash — don’t get it from a link provided by a random web page. Instead, visit the Real, Apple or Adobe sites to download it manually.

6. Finally, never use security software offered to you via unsolicited email or a popup window, or that suddenly appears on your PC. Such programs are almost always scams and often install malicious spyware, adware and viruses rather than cleaning them up. In general, stick with leading security brands like Symantec, McAfee, Zone Labs and Webroot. Check the software in the reviews section of PC Magazine or the CNET web site. If it isn’t covered there, it’s probably untrustworthy.

In tacit acknowledgment of IE’s shortcomings, Microsoft is currently mounting a crash effort to update the browser with something called Internet Explorer 7.

But it’s not ready yet. In the meantime, there are a handful of alternative browsers you can use every day instead of IE, on both Windows PCs and Macs — all of them superior to the current version of IE.

One caveat: Some Web sites, especially in the financial industry, have been constructed using proprietary features unique to Internet Explorer. Other browsers mainly stick to industry-standard features, meaning they can’t reproduce every component of these IE-oriented sites. It’s as if NBC decided to produce programming that would work properly only on, say, Sony TV sets. So the bottom line is this: If you are constantly using one of these nonstandard sites, you should continue using Internet Explorer, or at least keep it around for backup.

The best-known alternative to IE is Firefox, made by nonprofit Mozilla. Firefox is issued in nearly identical versions for Windows, Macintosh and the techie-oriented Linux operating system. By contrast, IE runs only on Windows. (Microsoft once made a Mac version of IE, but has discontinued it.) Another excellent choice is Safari, the browser by Apple that comes on every Mac, but has no versions for Windows or Linux. Opera, which comes in Windows, Mac and Linux versions, is also a fine alternative. One more option worth considering is the Windows-only Netscape browser.

These four options share two major characteristics. First, they’re generally more secure than IE. Theoretically, any browser can be attacked and used as a conduit for malicious software that can hobble your computer. Firefox, for example, has been forced to close numerous potential security holes. But IE is the least secure, for several reasons: It was designed in an era when security was less of a concern. Its very ubiquity makes it the favorite target of online criminals. And it uses a Microsoft-only technology called ActiveX that helps Web sites work better, but also allows malicious software to control aspects of the computer. The browsers mentioned above don’t use ActiveX, which is one reason they’re more secure, but it also helps account for their difficulty in handling some IE-oriented Web sites.

The second thing these alternatives have in common is tabbed browsing — the most important advance in browsers in years. This feature lets you open multiple Web sites simultaneously in the same window. Only one page is visible at a time, but the others are live and open behind it. Each is marked by a tab, like those found on paper file folders. To switch from the page you’re viewing to another, you click on a tab. You can also close any page without affecting the others, and if you follow a link on a tabbed page, it usually opens within the same tab. The real power of tabbed browsing comes in when you collect bookmarks (what IE calls “Favorites”) into folders. You can then click just once to open all the bookmarks in a given folder, each under its own tab. For instance, I have roughly 20 technology bookmarks in a folder, and I like to open them all at once in Firefox or Safari, the two browsers I use the most.

Why would you want to use a tabbed browser? First, it saves time. Second, it allows you to easily scan and compare related Web sites. Third, you can open a link in a new tab while keeping the original page open so you can easily return to it. All in all, I can’t imagine going back to Internet Explorer after using a tabbed browser. IE does allow you to open multiple Web pages, but only one at a time and in separate windows, which clog up your desktop and the Windows taskbar. That’s why even Microsoft recognizes the superiority of tabbed browsing and is building it into IE 7. (Note: Microsoft’s MSN online service currently offers an add-on that can bolt a simple version of tabbed browsing onto the current version of IE.)

Another feature the alternatives share, but IE lacks, is a built-in search box that appears right in the toolbar of the browser. This lets you perform a search without using an add-on toolbar or navigating to the home page of the search service.

If all the alternative browsers feature tabbed browsing, built-in search boxes and better security than IE, what are their pluses and minuses? Here’s a quick rundown of the three frontrunners.

– Firefox. This most popular alternative to IE is “open source,” meaning it’s open to improvement by any programmer anywhere. Thus, thousands of add-on features are available by installing free small software modules called “extensions,” which let you do things like download all links on a page with a single click or automatically fill out online forms; there’s even one that lets you view a Web page in IE. Firefox also offers a two-click method for clearing your browsing history and other evidence of where you’ve been online. Finally, its built-in search can be customized to use any popular search engine. That said, Firefox does have some rough edges. Closing tabs with the mouse is awkward the way it’s set up, and the command for viewing your history is illogically placed on the “Go” menu.

– Safari. This Apple browser includes an excellent built-in reader for so-called “news feeds” — summaries of blogs and news sites. It has a “private browsing” mode, which leaves no trace of where you’ve been online, and offers parental controls. It also does a great job of e-mailing entire Web pages, and it can save pages as PDF files, viewable on any computer. But Safari works exclusively on Macs, and its search box works only with Google.

– Opera. This long-established browser is loaded with features, including an excellent zooming capability, and if you have lots of tabs open, Opera can display them on multiple lines so you can more easily read their titles. But while Opera likes to claim it’s “the Fastest Browser on Earth,” in my tests it hasn’t proved itself swifter than Firefox.

You could download any one of these browsers for free today and be on your way to a better Web experience. Or you could wait for IE 7, which is likely to appear in the fall. It promises tabbed browsing, a built-in search box and a bunch of security improvements-that is, everything its rivals already offer.

Its visual display of files stored in a nested hierarchy of folders has worked pretty well — until recently.

In the past few years, computer hard disks have become huge, and average consumers have begun to accumulate thousands and thousands of files each year — far more than in the past. And that is making it much harder to find any particular bit of information buried in the old folder hierarchy.

Every time you plug a digital camera into a PC to transfer images, dozens or even hundreds of files can be added to your PC in one fell swoop. The same thing happens when you rip CDs or go on a photo downloading binge. Email is accumulating in staggering amounts, and just surfing the Web can add hundreds of files — silently cached copies of Web pages and images.

So the familiar file and folder system is buckling. Unless you’re the rare person who is meticulously organized, who creates a perfect system of orderly folders and recognizable file names, locating information on your own computer can be harder than finding it on the Web. There have always been search tools built into the Apple and Microsoft operating systems, but they were terrible — slow and inaccurate, covering only some kinds of data, not all. So you had to rely on separate search systems built into individual programs, such as email software.

But now a wave of new desktop search tools is becoming available, some built right into new operating systems and others available as add-ons. Big names are getting in the game — Apple, Microsoft, Google and Yahoo. I’ve been testing the leading candidates and previewing some future contenders. So here’s a rundown of the latest methods for finding all that lost or hidden information lurking on your hard disk.

Spotlight: This is the new universal, speedy search system built into Apple’s latest operating system for the Macintosh, called Tiger. Because it is an integral part of the operating system, which handles all files, Spotlight knows about all the key kinds of information stored on the computer. It can rapidly find words or phrases deep inside emails, Microsoft Office files, address books and calendars, Adobe PDF files and more. It can even probe the “metadata” — descriptive information — attached to song and picture files.

Spotlight is always available on the Mac, no matter what program you are in. You just click on a blue magnifying-glass icon at the top right corner of the screen, and a search field appears. As you type each letter of your search term, Spotlight begins generating results in a list of files that drops down almost instantly, organized by type of file. If you click on “Show All,” the list expands into a larger window where you can see more results, organized in almost any way you choose — by date, by person mentioned, by name or location on the computer.

On my Mac, I typed “Hawaii” into Spotlight and instantly got hundreds of hits. Every email mentioning the state came up, as did Word documents, Excel spreadsheets, the address entries of contacts who live there, calendar entries for my vacation in Honolulu and pictures of my trip. Spotlight even showed thumbnails of those pictures and, with one click, presented a slide show of the images. It also found the theme song from the old Hawaii Five-O television show in my music collection.

Because Spotlight is part of the operating system, it avoids one of the big flaws of add-on search systems — the need to periodically “index” new files in batches, a process that spins the hard drive continuously, sometimes for hours. Spotlight needs to do this only once, when you first install Tiger.

Longhorn: Microsoft plans to emulate Spotlight in the next version of Windows, code-named Longhorn. But it’s way behind Apple. Longhorn won’t reach consumers until the fall of 2006 at the earliest.

Based on previews of Longhorn I’ve seen, its planned built-in search system will also be fast and universal, and will avoid long indexing sessions. Microsoft also plans to allow more customization of searches, and many more instant previews of files, than Apple now provides. But these apparent advantages may evaporate.

By the time Longhorn arrives, Apple will likely have a second, even better, version of Spotlight.

Google: Until Longhorn arrives, Windows users must rely on add-on search software, and the best known is Google Desktop Search. It does the annoying indexing, but only when your machine is idle. Plus, it’s fast and fairly comprehensive, including even the contents of cached Web sites.

But the familiar Google search results page, which works so well for the Web, is very limiting for a desktop search. And the software offers only a crude way to sort the results and no way to preview content.

Yahoo: The big online service bought a desktop search engine from a company called X1 and re-branded it. This is a robust product, which indexes and searches many kinds of files and previews most of them in a built-in window. You can also take direct action on e-mails that turn up in your search — for instance, you can launch a reply right from within the search results.

The main problem with Yahoo’s offering, in addition to the fact that it isn’t buried deep in the operating system, is that it betrays its techie heritage. X1 was originally built for techies and hard-core search fanatics. Although Yahoo has cleaned it up a bit, the many choices and settings in the user interface may be daunting to mainstream users. Also, it has much more of the feel of a separate, heavy-duty program than the Apple or Google products.

MSN: The desktop search add-on from MSN prefigures what Longhorn will do, and it’s very good. Like Yahoo, it offers previews of most files right in its search results screen. And like Apple’s Spotlight, it is fast and presents a clean, simple interface that begins generating results as you type your search terms.

The main downside to MSN’s search is that in order to get it, you have to download and install a “toolbar suite” that lives in the Internet Explorer Web browser and adds a bunch of functionality that’s unrelated to search, which you might neither want nor need. Also, by default, MSN’s search product searches only your e-mail (which must be run by Microsoft products) and the My Documents folder. You have to tinker with settings to get it to search your whole computer, something all its competitors do by default. The limited search horizon cuts down on MSN’s indexing time and makes it look faster than it really is, but it will likely cause you to get only partial search results.

There are some other good search products out there from smaller companies, notably one called Copernic, by Copernic Technologies, which has a loyal following of users. Whichever you choose, once you trust desktop search, you may never again find yourself creating a subfolder.

There have long been computer viruses, but until the past couple of years, they were mainly a nuisance. Now they have grown into a serious problem — by one account there were 5,000 new Windows viruses discovered in the first six months of 2004. And the virus plague has been trumped by a new type of malicious software, spyware, which can track your activities, bombard you with unwanted ads, even steal your identity.

Spam has also grown exponentially, clogging e-mail boxes and carrying with it malicious software. For some people, e-mail has become a curse.

And that’s not all. Every minute of every day, hackers using automated software scan the Internet looking for computers vulnerable enough to invade and, in some cases, to surreptitiously take over. Without your knowledge, they can turn your computer into a “zombie” machine rigged to help them spread their nasty viruses, spam and spyware.

So for consumers and small businesses — everyone without a large IT department to manage security — the Windows computers they use have become huge burdens instead of helpful tools. If you do get a severe virus or spyware infestation, you may have to spend hundreds of dollars and many hours to wipe your hard disk clean and start fresh, quite possibly losing crucial data in the process.

And prevention is almost as painful as the disease, because the computer industry has so far come up with only half-baked and piecemeal solutions to these threats. You have to watch every move you make online and install a bunch of security programs, which require monitoring, constant updating and, often, annual fees.

Each of these security programs deals only with a narrow slice of the problem. Firewalls can keep out invaders, but they don’t stop viruses, spyware or spam. Antivirus programs don’t catch most spyware. Antispyware programs don’t stop viruses. And neither stops spam. For that, you need anti-spam software, which does nothing about viruses or spyware that invade your system through avenues other than spam.

You can buy “suites” that combine all these programs, but they are really just bundles of separate applications of widely varying quality stuffed into the same box.

It’s as if you needed a separate burglar alarm system, each with its own control panel, password and monthly fee, for every door and window in your home.

What users need is a simple, all-encompassing security service that would deal with all these threats with minimal user involvement. For now, though, you’ll have to do it yourself.

So here’s my quick guide to Windows security measures. Some of the products I recommend below are free, but others cost money. I like free stuff as much as the next guy, but I don’t believe security is an area where price should govern. You don’t want to entrust your computer’s security to some unknown software author, or even to a well-meaning individual or very small outfit that lacks the resources to keep up with the threats.

Download and install all the security fixes Microsoft issues for Windows. If you have Windows XP, set it to automatically fetch and install these patches (you can do this by clicking on the “Automatic Updates” or “Security Center” icons in the Windows control panel). You should also probably install the massive Service Pack 2 revision of Windows XP, which plugs many security holes. But back up your data first. A significant minority of users have reported big problems with SP2.

Stop using Microsoft’s Internet Explorer Web browser, which has become a four-lane highway for malicious invaders. I recommend instead Mozilla Firefox, which is free at www.mozilla.org [http://www.mozilla.org]. I use it all day, every day.

Windows comes with a firewall program, designed to keep out hackers. But in most versions of the operating system, it’s hard to turn on and configure. Even the improved firewall in the new SP2 revision of Windows XP is inferior to several third-party products. I recommend, and use, ZoneAlarm, a free firewall from Zone Labs, available at www.zonelabs.com [http://www.zonelabs.com]. There are some fancy paid versions of ZoneAlarm, which are also fine, but if you want the free one, you’ll have to look hard on the Web page.

Software to stop spyware is still in its infancy, so I suggest keeping two or three anti-spyware programs on hand. Each program will likely find spyware the others miss. But I recommend relying most on the one I use, Webroot’s Spy Sweeper, available at www.webroot.com [http://www.webroot.com]. It costs $30, including a year of updates, and runs all the time to block incoming spyware. To back up Spy Sweeper, go to www.download.com [http://www.download.com] and get two free programs: Ad-Aware, and Spybot Search and Destroy. Use these for manual scanning.

I recommend Norton AntiVirus from Symantec. It costs $50, including a year of updates. But it works well and has a good automatic updating system. I have been receiving many reports of problems with Symantec’s customer service, so I may have to change my recommendation down the road. But for now, I prefer Norton, and I use it myself.

No antispam program I have tested is wholly satisfying, but I suggest one of two. The first is MailFrontier Desktop, available for $30 at www.mailfrontier.com [http://www.mailfrontier.com]. The second is SpamSubtract, from Intermute, available for $20 at www.spamsubtract [http://www.spamsubtract]. com. They are very different, and each has its strengths and weaknesses. I oscillate between the two every six months or so.

Beyond installing, monitoring and updating all this software, you need to be careful online. Don’t open email attachments you don’t expect and that come from strangers. They may contain viruses or spyware. Don’t download software unless you really need it and are 100 percent certain of the author’s trustworthiness. It could be an infection in disguise. Never click on a link in an e-mail purporting to be from a financial institution, even if it’s your own bank and it looks official. It could be a scam to steal your identity.

And if you’re totally fed up with the security crisis but want to continue using your computer for common tasks, consider dumping Windows altogether and switching to Apple’s Macintosh, which uses its own operating system, called OS X. There has never been a successful virus reported on OS X, and there is little or no spyware for the Mac.

In my view, Macs have better hardware, a better operating system and better bundled software than Windows PCs. They are as good as, and often better than, Windows PCs at e-mail and Web surfing; at word processing and other productivity tasks; and at handling digital photos, videos and music. And most popular Windows file types open right up in Mac programs, without the need for any conversion or translation.

Stay safe out there.