Vista is much prettier than previous versions of Windows. Its icons look better, windows have translucent borders, and items in the taskbar and in folders can display little previews of what they contain. Security is supposedly vastly better; there are some new free, included programs; and fast, universal search is now built in. There are hundreds of other, smaller, improvements and additions throughout the system, including parental controls and even a slicker version of Solitaire.

After months of testing Vista on multiple computers, new and old, I believe it is the best version of Windows that Microsoft has produced. However, while navigation has been improved, Vista isn’t a breakthrough in ease of use. Overall, it works pretty much the same way as Windows XP. Windows hasn’t been given nearly as radical an overhaul as Microsoft just applied to its other big product, Office.

Vista’s Flip 3D feature lets you scroll through images of currently running programs. The sidebar (right) contains miniapplications. The Windows Photo Gallery (left) is for organizing and editing photos.

Nearly all of the major, visible new features in Vista are already available in Apple‘s operating system, called Mac OS X, which came out in 2001 and received its last major upgrade in 2005. And Apple is about to leap ahead again with a new version of OS X, called Leopard, due this spring.

There are some big downsides to this new version of Windows. To get the full benefits of Vista, especially the new look and user interface, which is called Aero, you will need a hefty new computer, or a hefty one that you purchased fairly recently. The vast majority of existing Windows PCs won’t be able to use all of Vista’s features without major hardware upgrades. They will be able to run only a stripped-down version, and even then may run very slowly.

In fact, in my tests, some elements of Vista could be maddeningly slow even on new, well-configured computers.

Also, despite Vista’s claimed security improvements, you will still have to run, and keep updating, security programs, which can be annoying and burdensome. Microsoft has thrown in one such program free, but you will have to buy at least one more. That means that, while Vista has eased some of the burden on users imposed by the Windows security crisis, it will still force you to spend more time managing the computer than I believe people should have to devote.

Here’s a quick guide to the highlights of the new operating system.

Versions and Upgrading

Vista comes in six versions, two of which are primarily aimed at consumers. One, called Home Premium, is the one most consumers will want. It contains the full Aero interface, and it includes the functionality of Windows Media Center and Windows Tablet edition, which have been discontinued as separate products. Home Premium costs $239, or $159 if you are upgrading from an earlier version of Windows. It will come preloaded on most midrange and some high-end consumer PCs.

The other main consumer edition of Vista is the stripped-down version, called Home Basic. It includes the improved security and search but leaves out the new Aero interface and the Media Center and Tablet functions. It will be preloaded on low-price PCs. Home Basic will cost $199, or $100 for upgraders.

A third version, called Ultimate, will wrap up everything in Home Premium with some additional features from the business versions of Vista. This is for power users, and it is likely to be preloaded on high-end PCs. But some regular users may need Vista Ultimate if their companies have particular network configurations that make it impossible to connect to the company network from home with Home Basic or Home Premium. Vista Ultimate will cost $399, or $259 as an upgrade.

Even if you buy the Home Premium or Ultimate editions, Vista will revert to the Basic features if it detects that your machine is too wimpy to run the new user interface.

For most users who want Vista, I strongly recommend buying a new PC with the new operating system preloaded. I wouldn’t even consider trying to upgrade a computer older than 18 months, and even some of them may be unsuitable candidates. Microsoft offers a free, downloadable Upgrade Advisor program that can tell you how ready your XP machine is. It’s available at: microsoft.com/windowsvista/getready/upgradeadvisor.

If you bought a PC in the past few months, and it had a “Vista Capable” sticker on it, it should be able to run at least Home Basic. If it was labeled “Premium Ready,” it should be able to handle Premium and probably Ultimate.

Microsoft says that Home Basic can run on a PC with half a gigabyte of memory and that Premium and Ultimate will work on a PC with one gigabyte of memory. I strongly advise doubling those numbers. To get all the features of Vista, you should have two gigabytes of memory, far more than most people own.

Even more important is your graphics card, a component most people know little about. Home Basic can run on almost any graphics system. But Premium and Ultimate will need a powerful, modern graphics system to run well.

Performance

I tested Vista on three computers. On a new, top-of-the-line Hewlett-Packard laptop, with Vista preinstalled, it worked smoothly and quickly. It was a pleasure.

On a three-year-old H-P desktop, a Vista upgrade installed itself fine. But even though this computer had a full gigabyte of memory and what was once a high-end graphics card, Vista Ultimate reverted to the Basic user interface. And even then, it ran so slowly and unsteadily as to make the PC essentially unusable.

The third machine was a new, small Dell XPS M1210 laptop. In general, Vista ran smoothly and well on this Dell, but some operations were annoyingly slow, including creating a new message in the built-in Windows Mail program. This surprised me, because the Dell had two gigabytes of memory and a fast processor.

Security

Microsoft says Vista is much more secure than any other operating system. But this is hard to prove, especially at the beginning of its life, when few hackers and malefactors have access to it. One visible security feature asks for your permission before you do potentially dangerous tasks, like installing new software. This is a good thing, and it’s been on the Macintosh for years. But unlike the Mac version, the Vista version of this permission feature doesn’t necessarily require you to type in a password, so a stranger or a child using your PC could grant permission for something you yourself might not allow.

Vista also has built-in parental controls so you can restrict what a child can do on the computer. This is also already on the Macintosh, though the Vista controls are more elaborate.

Microsoft includes a free antispyware program in Vista, called Windows Defender. But PC Magazine regards it as inferior to paid programs like Spy Sweeper and Spy Doctor. So you may want to buy one of these. You should also buy an antivirus program, which isn’t included.

User Interface

The new Aero interface is lovely, and it makes using a PC more pleasant and efficient. It apes some elements on the Macintosh but retains a distinct look and feel. Icons of folders look three dimensional, and they pop. Most file icons are thumbnails that show a tiny preview of the underlying document.

Like the rest of Vista, the Start Menu has a prettier, more refined look.

The old hourglass icon that appeared during delays has been replaced by a gleaming, spinning blue circle. The cutesy names for standard folders, like “My Pictures,” have been changed to simpler ones, like “Pictures.”

As on the Mac, you can now drag favorite folders into a list at the left of open windows, so it’s easy to get to them.

A new feature called Flip 3D shows a 3D view of all the programs you’re running and lets you scroll through them. It’s like the Mac’s excellent Exposé feature, though not quite as handy.

Another new feature, called the Sidebar, is a vertical strip at the side of the screen that can contain tiny programs, called Gadgets, displaying things like favorite photos, news headlines, stock prices and the weather. Once again, this is awfully similar to a Macintosh feature called Dashboard, which displays tiny programs called Widgets.

Some familiar Windows features have new names. The old Display control panel, where you chose screen savers and desktop pictures, is now called Personalization. The Add or Remove Programs control panel is now called Programs and Features.

Search

Like the Mac, Windows now has rapid, universal, built-in search, a very welcome thing. The main search box is contained at the bottom of the Start menu, and it works well. Other search boxes appear in every open window.

You can also save searches as virtual folders, which will keep collecting files that meet your search criteria. This is another feature introduced earlier by Apple.

Built-In Programs

The Outlook Express email program has been given a face-lift and renamed Windows Mail. But it’s pretty much the same, except for a new junk-mail filter. The Windows Address Book has been renamed Windows Contacts and, oddly, turned into a sort of file folder.

The latest version of the Internet Explorer Web browser, with tabbed browsing, is included, though it’s also available for Windows XP.

As on the Mac, Windows now has a nice, centralized Calendar program. And there’s a new photo-organizing program, Windows Photo Gallery, but it’s inferior to Apple’s iPhoto because it doesn’t allow you to create photo books, or add music to slide shows. There’s also a pretty rudimentary DVD-burning program.

The familiar WordPad program can no longer open Microsoft Word files (ironically, Apple’s free built-in word processor does).

Gradually, all Windows computers will be Vista computers, and that’s a good thing, if only for security reasons. But you may want to keep your older Windows XP box around awhile longer, until you can afford new hardware that can handle Vista.

• Email me at mossberg@wsj.com.