Don't blame Vista - not that I am a fan, but your games are probably not "Vista Ready". Revert to your former OS and enjoy your games, or get the "vista Edition".
I have a Dell XP laptop with a Intel 945GM 256mb graphics card and till recently all my video games used to work just fine. I used to play Flight Simulator 2004, Age of Empires 3 etc. without any problems. But just last week I upgraded my laptop to Vista and since then my games performance has gone horribly bad. In Flight Simulator for example, I can't get more than 1-2 fps. Age of Empires 3 actually says "You have a 32mb graphics card so game won't work, sorry" or something like that when I'm quite sure I have a 256mb graphics card! Some other game said the same thing. Anyone know why this is happening? Is there some problem in Vista that is causing my games not to "detect" my graphics card or something? Incidentally, the Aero thing on Vista works fine so I'm not sure what exactly is going on.