Starting in January, six months earlier than promised, Apple began switching the Mac to the very latest Intel processors-allowing higher speeds at lower temperatures compared with the previous IBM chips. Apple’s sleek, slim computers can run faster without bulking up for extra fans or heat-dispersion space.

That change, in turn, enabled Apple to stun the world in April when it announced a free utility that permits the Intel-based Macs to run Windows as a complement to the Mac operating system. With this new software, called Boot Camp, a Mac user can start up the computer either as a Mac or as a Windows machine. That means people who resisted switching to the Mac because they need to run one or two programs available only in Windows can now convert without hesitation.

America’s slimmest brand-name desktop, the dazzling white iMac, now runs faster with Intel chips yet retains its slender form. So does the thin, aluminum-clad 15-inch MacBook Pro laptop, a renamed version of the PowerBook. Like its Mac siblings, the tiny Mac Mini desktop now includes an Intel processor that incorporates two “cores,” the equivalent of two processors in one.

These Intel models are Macs through and through because they still run Apple’s Mac OS X operating system, Tiger — which is so far ahead of Windows that it already contains the key features Microsoft is promising for its much-delayed new version of Windows, Vista, due in January.

But now Macs can run Windows as well. Apple’s other models should be converted to Intel by late 2006. They include the 17-inch-screen version of the MacBook Pro laptop, the thinnest and lightest portable available; the entry-level MacBook laptop, formerly called the iBook; and the top-of-the-line PowerMac towers.

The new Mac lineup doesn’t include some categories of computers offered by the likes of Dell and HP. For instance, Apple lacks an ultralight laptop like the 2.5- to 3.5-pound Windows models from Sony and Toshiba. It doesn’t offer gaming-specific desktop towers or big laptops, like those from Alienware and Dell. And it doesn’t offer models with built-in TV tuners and TiVo-like digital video recorders, like those available from most PC makers.

Also, while Macs now use standard ports and connectors, which can accommodate most any printer or scanner, they omit a couple of common features found on many Windows machines. They’re not equipped with readers for camera memory cards, and the laptops don’t have built-in receivers for the new, high-speed cell phone data networks. You can add both of these features as external add-ons, at extra cost.

On the other hand, Macs running the OS X operating system aren’t susceptible to the many thousands of viruses and spyware programs that plague Windows computers; most Mac users don’t bother to run antivirus and antispyware software.

Then there’s price. Years ago Macs cost much more than Windows PCs. That’s no longer true. The iMac is priced comparably to identically equipped Windows machines, though no similar Windows desktop is as slim. Mac laptops can run a few hundred dollars more than Windows models, though comparable Windows laptops tend to be thicker and heavier, with lower-quality screens.

But Apple has no offerings cheaper than its $599 base Mac Mini, which lacks a keyboard, monitor and mouse. It doesn’t play in the market’s bargain-basement segment, where Dell, HP and others have stripped-down models that sell for under $400.

Here’s a quick guide to the fresh Mac models, and to their new ability to run Windows.

DESKTOPS

The iMac. This is Apple’s flagship product, its main consumer desktop and, in my view, the best available consumer desktop. At first glance, it looks like just a sexy, white, flat-panel monitor. But there’s a powerful computer packed behind the screen, which can also run Windows. The iMac also has a built-in video and still camera, plus a special operating mode called Front Row that allows you to play music, videos, DVDs and photo slide shows from across a room, using an included remote control. The iMac starts at $1,299, complete with a built-in flat-panel screen.

The Mac Mini. The smallest desktop computer I’ve ever tested, at 6.5 inches square and 2 inches high. Yet it’s a full-fledged Mac, complete with the latest Intel chips, that can also run Windows. Starting at $599, the Mini includes Front Row with remote control and is often bought for connecting to a TV as a media hub.

The Power Mac. This is a heavy-duty tower, favored by graphic artists, musical composers, video producers and scientists. It has yet to be upgraded to Intel processors, but currently can be ordered with as many as four IBM G5 cores. For most consumers, it’s overkill. It starts at $1,999, without a monitor.

LAPTOPS

The MacBook Pro. Apple’s top laptop, a renamed, reengineered version of its famous PowerBook that looks and works pretty much the same-only faster. Though currently available only with a 15-inch screen, for $1,999, a 17-inch model may roll out. It’s not clear if the 12-inch PowerBook, which remains on sale at $1,499, will also be replaced.

The main difference between MacBook Pros and PowerBooks? The former use the new Intel processors, have built-in video cameras, and feature Front Row and the remote control. Oh, and they can run Windows. The MacBook.This is the rumored name for a new entry-level Intel-based laptop that will soon replace the iBook. It should be much faster and also be able to run Windows. Meanwhile, the iBook remains on sale, starting at $999. It uses the older IBM G4 processor.

WINDOWS ON A MAC

The new Intel-based Macs can run Windows via Boot Camp, a free Apple utility that overcomes some subtle hardware differences between the Intel-based Macs and standard Windows computers.

After you run Boot Camp, you simply buy a copy of Windows XP (Apple won’t sell or support Windows) and install it as you would on any regular Windows computer. You must use a full, nonupgrade copy of Windows that includes the update Microsoft calls “SP2.” These versions of Windows cost $200 to $300.

Once Windows is installed on a Mac, each time you start up you can choose whether to run the Mac OS or Windows. Only one operating system can be used at a time, and each controls its own walled-off section of the Mac’s hard disk.

In my tests, an Intel iMac running Windows performed like a fast, normal Windows computer and ran every Windows program and hardware device I threw at it.

Apple isn’t abandoning its operating system or switching to Windows. It’s making it easy to run Windows on a Mac in hopes of tempting potential switchers who would use the Mac OS most of the time, but need to shift to Windows periodically to run programs that don’t have Mac equivalents.

Macs aren’t for everyone. But they are superior computers, and with the new Intel chips and Windows capability, they are more attractive than ever.

This year, however, Microsoft will up the ante with a new version of Windows called Vista. Due in the fall, in time for holiday computer shopping, Vista is an effort to make Windows truly secure from the ground up, while also making it easier to use and pretty enough to rival Apple’s current version of OS X, Tiger. (Apple is planning yet another new edition, called Leopard, due around the same time.)

Vista will be the most dramatic upgrade to Windows in more than a decade. But there will be a price for Vista’s improvements — most current PCs won’t be able to take advantage of all its features. To get full use out of the new system, you will very likely need to upgrade or replace your current computer. Vista will adapt to older or less powerful machines by disabling some of its features, but that’s likely to be unsatisfying for many users. Also, as of this writing, Microsoft is planning to sell Vista in as many as seven different configurations for different types of users. That will be not only confusing, but if you select the more capable configurations, probably expensive, too. (Microsoft hasn’t released pricing yet.)

So here’s a preliminary look at Vista’s major new features, as well as some guidance on hardware. Microsoft’s mantra for Vista is “Confident, Clear and Connected.” By “Confident,” the company means that it promises to clean up the security mess that has been the main headache for users of Windows. Microsoft says Vista will be much harder to hack into, and much less prone to viruses and spyware, than today’s Windows. For instance, Vista users will be asked for their user name and password anytime software is being installed –designed to prevent the surreptitious software installations that plant spy-ware on a PC. And Vista will have built-in systemwide parental controls, so you can limit what your child can see and do on the computer. Both features are already built into Apple’s Tiger and work well, so if they are executed properly on Vista, they should be a boon.

By “Clear,” Microsoft is referring to new ways of finding and visualizing your files. Vista will have rapid, modern, built-in desktop searching. And it will have something called “virtual folders” that capture all files meeting certain criteria you can set, no matter where you store them. For instance, you could set up a virtual folder to show all files and e-mails mentioning a certain person or topic. Again, both features are already in Apple’s operating system, where they have proved popular. Some editions of Vista will also incorporate the features of today’s Windows Media Center edition, including the ability to play and record TV programs.

The “Connected” promise from Microsoft includes a centralized synchronization feature, like the one already present on the Mac, that can keep data in sync on cell phones and PDAs. Vista will also look dramatically better — and more like Mac software — with 3D icons, transparent windows and tiny previews of file contents.

So what kind of hardware will you need for all this? Well, Vista won’t work well with the processors sold in today’s budget PCs. I suggest you consider a new computer with at least a midrange processor, and preferably a so-called dual-core processor, which packs two brains into its innards, though a single-core model will do. You might even look for a processor capable of handling future software called “64-bit,” though it’s not absolutely necessary.

Memory will also be crucial for Vista. I expect Microsoft to recommend 512 megabytes, but since the company tends to understate memory requirements, I suggest a full gigabyte, far more than what’s on the average PC today. You’ll also need a bigger hard disk, especially if you want to use the new TV-recording capabilities that will be built into some editions of Vista. I suggest at least 160 gigabytes. Luckily, large hard disks are now pretty inexpensive.

Likewise, video capability will be key to utilizing Vista’s new visual effects. Today’s PCs often use integrated graphics chips, which are pretty basic and drain memory. That won’t cut it for Vista, at least until integrated graphics chips are beefed up next fall. If you seek a Vista-capable machine before then, look for one with a separate graphics card with its own dedicated memory, preferably 128 megabytes, though 64 will do.

Vista will boost DVD recording — it will support the new, high-definition DVDs currently in development and make it easier to burn DVDs for both multimedia and file backup. You’ll need a high-end DVD-recording drive to reap the rewards.

I can’t say how good Vista will be until I test and review the final, or near final, product, in late summer. But from the demos I’ve seen, Vista has great promise — if you have the right hardware.

But as slick as it is, Apple’s latest baby isn’t the only path to portable digital video available to consumers. Others got there first. All, including the new iPod, suffer from a dearth of legal downloadable content, but that has begun to change as Hollywood and the television networks seem willing, suddenly, to sell individual episodes of television series.

Here’s a quick guide to some leading portable video devices.

Old reliables: All the new video gadgets should be measured against portable DVD players and laptops with DVD drives. The portable players combine relatively large screens with thin, light designs and low prices. The laptops are larger and pricier, but their advantage is that many people carry them anyway for other purposes. And both have a vast library of cheap content to draw from: DVDs. The downside is that you have to lug along a selection of disks.

Portable media centers: These are gadgets that are smaller than a laptop, but larger than an iPod. They use Microsoft software that mimics the nice user interface in its Media Center version of Windows. Leading examples are the Samsung Yepp PMC and the Creative Zen PMC, both of which cost $500, which is more than even the priciest video iPod. They have larger screens than the iPod, but smaller storage capacity. Little legally downloadable content is available for the PMCs, but users can transfer to them TV programs they have recorded on high-end Media Center PCs.

Sony: The new PSP, or PlayStation Portable, from Sony, has a large, bright screen that does a great job showing videos, even though it is primarily a game machine. This slick, black $250 gadget is handsome, but unlike the iPod, it’s too large to carry in a pocket. Also, getting video into the PSP is clumsy and expensive, mainly because it lacks either a hard disk or a standard DVD drive. You have to buy movies on special, small copy-protected disks. And if you want to transfer videos from a computer, you have to buy a high-capacity memory stick.

Archos: This small company has been a pioneer in handheld video and makes several models, in a wide variety of sizes and capacities, that cost from $500 to $800. In general, Archos buyers have been early-adopter techies and videophiles willing to do what it took to collect video clips and move them onto the Archos gadgets. But the company is now going mainstream, through a deal with EchoStar, the satellite TV firm. EchoStar will sell three Archos models, rebranded as PocketDISH players, that can copy and play back TV shows recorded by EchoStar set-top boxes with digital video recorders inside. The PocketDISH players range from $300 to $600.

iRiver: The Korean maker of portable music players has just introduced a tiny video player, smaller but thicker than the video iPod, called the U10. It’s a handsome gadget with a clever user interface: You select functions by pushing on the edges of the screen. But it has a meager storage capacity, only a gigabyte, in a top-of-the-line model that costs $250, just $50 less than a video iPod with a larger screen and 30 times the storage.

Apple: The video iPod, which Apple calls simply the iPod, comes in two models: a $299 version with 30 gigabytes of storage and a $399 model with 60 gigabytes. Like all iPods, it is beautiful, easy to use, and it’s thinner and lighter than the prior generation. Short videos look great on its screen. Apple is selling episodes of two hit TV shows, Desperate Housewives and Lost, for $1.99 each. Again, content for all these gadgets is sparse today. But as the availability of legal video downloads grows, so will the rationale for buying a portable video player.