"You can't make an omelet without breaking a few eggs." If that's not Microsoft's motto, maybe it should be. Each successive version of Windows may be better than the previous one, but inevitably winds up "breaking" hundreds of programs, utilities, and drivers that used to run fine.

To soften the blow, Microsoft has pulled every trick in the book to make older, pre-Vista programs run successfully. For example:

16-Bit Programs

A 16-bit program is one that's so old, it was written when Windows 3.1 roamed the earth and George Bush Sr. was president. (Programs written for Windows 95 and later are known as 32-bit programs; Vista can even run 64-bit programs.) But amazingly enough, Windows Vista can run most of these programs. It does so in a kind of software simulatora DOS-and-Windows 3.1 PC impersonation called a virtual machine.

As a result, these programs don't run very fast, they don't understand the long filenames of modern-day Windows, and they may crash whenever they try to "speak" directly to certain components of your hardware. (The simulator stands in their way, in the name of keeping Windows stable.) Furthermore, if just one of your 16-bit programs crashes, all of them crash, because they all live in the same memory bubble.

Even so, it's impressive that they run at all, 10 years later.

DOS Programs

These programs are 16-bit programs, too, and therefore they run just fine in Windows, even though DOS no longer lurks beneath the operating system.

To open the black, empty DOS window that's familiar to longtime PC users, choose Start->All Programs->Accessories->Command Prompt.

Programs Written for Windows 95, 2000, XP, and So On

In principle, programs that were written for recent versions of Windows should run fine in Vista. Unfortunately, some of them contain software code that deliberately sniffs around to find out what Windows version you have. These programs (or even their installer programs) may say, "Windows what?"and refuse to run.

Fortunately, the Properties box of every program (or program shortcut) offers you the opportunity to fool such programs into believing that they're running on a Windows XP machine, Windows 2000 machine, or whatever.

• You're much better off securing an updated version of the program, if it's available. Check the program's Web site to see if a Vista-compatible update is available.

• Don't try this trick with utilities like virus checkers, backup programs, CD burning software, and hard drive utilities. Installing older versions of these with Vista is asking for disaster.

• If the program you're trying to run is on a CD or on a hard drive elsewhere on the network, you won't be able to change its properties using the steps described. Instead, choose Start->Control Panel. Click Programs, and then click "Use an older program with this version of Windows." A series of wizard screens explains the concept of compatibility-fooling, and then lets you choose the program you'd like to fool.

• The "Run this program as an Administrator" checkbox can also be a magical pill that lets an older program run. In effect, though, you're overriding one of Vista's new security features in the process.

  That's why, the next time you open the program, a UAC message appears, asking if you're sure you want this program to be allowed to run. Click Allowif you're darned sure.