On the other hand, I have drawers full of PC-DOS programs from the early 1980s that run fine under XP. Not to mention lots of early Windows programs. Not that I like running old programs, but some of them were database programs, and it is nice to know that the data can still be retrieved.
I an old program that won't even install on anything besides FAT16. I'd have to crank up Windows 95 on FAT16 under VirtualPC to get it to work. I also have some DOS games that won't work under XP, and some Windows 9x games that are very buggy under XP. But that's why I have VirtualPC.