Yeah man the problem is with the game code, since the demo was compiled on windows XP it only works with XP and such, since the 1.3.1 patch was compiled with XP and vista it works with both.
I didn't make it!
Umm:uhm:...guys lol. From what i have been told, the demo version of doom is only for xp...the demo can't recieve entire patches due to the lack of certain game files.:o but the retail version should work fine.:)