i tried running Vista on my onboard intel Extreme Graphics 2 (865GBF). For this i removed my FX 5900XT graphics card, & rebooted, then, Vista crashed with a BSOD, as i forgot to uninstall the graphics card driver.
I booted in safe more, uninstall the nvidia drivers & then on the next boot, Vista booted properly in Windows classic UI, the performance was slow, so...i guess intel extreme graphics 2 & GMA 900 are out of league to run Vista properly. Vista was using the inbuilt graphics driver of this case
Those who wants to check weather their PC can run Windows Vista should check the Windows Vista upgrade advisor