I have done so much testing for microsoft windows vista that i should warn you.
I have come across problems with older video cards , onboard sound, onboard video, scanners and even some printers.
if your pc is running windows me or below don't bother upgrading to vista to be honest your just wasting your money.
to find out whats in your pc download and run everest home.
http://www.majorgeeks.com/download4181.html
that little program should be able to give you a very good detailed list of whats in your pc.
call up your motherboard, cpu , sound, video, memory.
if you like post that info here and i will tell you if its worth your while upgrading to vista or not.