Microsoft Advices to Avoid Integrated Graphics Cores for Windows Vista:

"‘The new graphics capabilities in Windows Vista will require a powerful graphics engine if you want to take full advantage of all the new and cool stuff, such as the new Aero Glass look. You probably want to avoid the low-end of the current GPU range and make sure you get a GPU that supports DirectX 9 and has at least 64MB of graphics memory,’ a special article by Microsoft dedicated to hardware requirements of Windows Vista explains."

(Via Bink.nu.)