windows Vista & XP

will Vista be able to run XP programs ?

Some programs will not work but most of them should have no serious problems.

Also keep in mind that if a program does not work that it's developer will probably release a patch as long as the program is still developed.

I think so, but there will be some programs and games that won't run on XP anymore.

MS is working on virtual machines software, more or less a kind of emulation, (more exactlly virtualization), since they bought Connectix (and so Virtual PC) and from what I read on Aaron Giles site. I guess this is the way they have choosen for compatibility issues.

http://www.microsoft.com/windows/virtualpc/previous/default.mspx
http://www.aarongiles.com/

AFAIK the more a program interacts with hardware, more chances exist for incompatibility

thank you everyone