As far as I can tell, any games designed to work with XP will still work with 7. However, Windows 98 and earlier games, specifically the ones that either have a 16 bit installer or are completely 16 bit, won't work on 64 bit Windows 7. These games are often old enough that they don't require any sort of 3d accelleration, and in that case, a virtual machine such as Windows XP mode can help. I have a virtual machine with a Windows 95 install specifically for this sort of situation. By the way, if you have an old copy of Windows, you don't need to shell out for XP mode -- the program itself is free, the extra cost is for a Windows XP license.