Windows XP Pro: The Missing Manual, Second Edition

Running Pre-XP Programs

As any Windows 2000 user can tell you, stability has its price. For years, people who ran Windows 2000 enjoyed far fewer system crashes than Windows Me people did—but they were limited to a much smaller set of compatible programs. (Barney the Dinosaur CDs, for example, simply wouldn’t run on Windows 2000.)

Although it’s based on Windows 2000, Windows XP isn’t quite as limiting to your software library. Microsoft has pulled every trick in the book to make older, pre Windows XP 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.) Bit amazingly enough, even Windows XP can run most of these programs. It does so in a kind of software simulator—a 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 the 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 XP 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, ten years later.

DOS Programs

These programs are 16-bit programs, too, and therefore they run just fine in Windows ...