Drivers. They have caused many problems. In your case, get the Vista drivers for the graphics card. You probably reqiure an update of the BIOS too.
I successfully upgraded from XP Home to Vista Home OS. A problem that I am having is that my screen resolution keeps changing so that most of the color is faded. Sometimes the whole screen will black out before the resolution changes. There doesn't seem to be any pattern so I don't k now what is causing this.
Any help is appreciated, thank you.