Washington  - Buy a new copy of Windows Vista or a new computer today, and you'll have a decision to make: Should you go for the 64-bit version of Windows Vista, or the 32-bit version?

We've all been using various 32-bit versions of Windows for years now, but clearly the future belongs to 64-bit computing. What do you need to know before you get a jump on destiny? Here are some answers.

Q: Why would I want to run 64-bit Windows?

A: You'll get access to more system memory. The 32-bit versions of Windows - Vista and XP - can access a maximum of 4 gigabytes (GB) of system memory. In practice, however, some of that system memory is reserved for the operating system and other processes, so your applications end up with significantly less. It's not uncommon for a computer with 4 GB of memory installed to have only 3 GB available once the operating system and other processes stake their claim to the memory.

While 3 GB may have seemed like a lot of memory a few years ago, today all you need to do is run a memory-hungry photo program, load a half-dozen large files, and you could be pushing the limits of your installed memory.

The 64-bit version of Windows Vista can access much more than 4 GB of RAM. Vista Ultimate, Enterprise, and Business can access 128 GB of RAM. Home Premium can access 16 GB, while Home Basic will max out at 8 GB.

Having the ability to access more memory in your computer gives you a couple of advantages. First, you can load more applications and more files within those applications. Second, your overall computing experience should be smoother, since swapping from one application to another will hopefully take place in memory and not rely on caching data to the hard drive, which slows you down.

Q: Is the 64-bit version of Windows Vista faster than the 32-bit version?

A: Theoretically, the 64-bit version of Windows should allow your computer to process twice as much data as a 32-bit operating system in the same amount of time. In practice, though, you will not see a doubling of performance with a 64-bit operating system, in part because there are so many variables - both in hardware and software - that must be optimised for 64-bit computing.

In fact, if you run the 64-bit version of Windows with only 4 GB of system memory, you may find that the computer runs a tad slower than with a 32-bit operating system due to the way computer instructions are stored in memory in 64-bit systems - essentially, they take up more space. So you should have more than 4 GB of memory when running a 64-bit version of Windows. If you do, you should see a slight real- world performance improvement when running a 64-bit application.

Q: Are there any disadvantages with the 64-bit version of Windows?

A: Your primary concerns should be software compatibility and drivers. Since 64-bit operating systems are not yet used as widely as 32-bit versions, not all computer software vendors have gotten around to ensuring that their programs run properly under 64-bit Windows. Many have, though. So before you install 64-bit Windows or buy a computer with it pre-loaded, check your major software applications to ensure that they're compatible.

You'll also want to make sure you can use all of your peripherals - printer, scanner, Webcam - with 64-bit Windows. And that means checking with the manufacturers to see whether 64-bit versions of the appropriate driver software are available.

Q: Do I need a special computer to run 64-bit Vista?

A: No. Any computer you buy today - whether it comes with an Intel processor or one from AMD - will run 64-bit operating systems. If you have an older computer, find out which processor is in it, and check the manufacturer's Web site to determine whether is 64-bit capable.

Q: I bought Windows Vista Home Premium, and only the 32-bit version came in the box. Do I have to pay extra for the 64-bit version?

A: No. Microsoft will ship you the 64-bit version at no charge. The rule is that you can only run one of the versions, though, not both. To get the 64-bit version after you've already purchased the 32-bit version, go to the "64-bit DVD" section at the bottom of this page, and follow the instructions: http://www.microsoft.com/windows/windows- vista/compare-editions/64- bi t. aspx.

Q: Is Microsoft phasing out 32-bit Vista?

A: No. But the company has announced that it is transitioning to 64-bit operating systems and applications beginning in 2009. Already some Microsoft products are 64-bit only.

Windows 7, Vista's successor, will be released in both 32-bit and 64-bit versions, but in the server operating system arena, Microsoft has indicated that the current Server
2008 product will be the last 32-bit server operating system. One can reasonably expect the emphasis to shift heavily to 64-bit computing over the next year.

--- Have a computer question? Send it to the Computer Helper at jayd@csi.com. (dpa)