Hi, are you using a built-in video chipset on the motherboard or do you have dedicated graphics card?
If it's the first, as fjiekie said, find the manufacturer and go to their website.
If you don't know (not sure) who the manufacturer is, go to Start > Run > type in: dxdiag > Hit ok (> hit yes if the computer comes up with a dialog box)
in the dxdiag window that opens there's a line around the middle of the window that says "System Manufacturer:"
If you can't find anything useful on the manufacturer website, let us know, there's a few other places you can try checking for drivers.