Hey
What you need to do is boot it up in safe mode I think you press F8 when booting up then when it has started up it should use the minimal settings, but it should give you your picture on the whole screen. If it does do this then change it to the best setting you can and that may well solve it. All I can say is give it a whirl. It's the only other option I can think of because all my other solutions have been posted by others. If you're desperate you could possibly try resetting your bios (you might have a clear cmos button on your motherboard or unplug pc for 20 secs) Or try taking the AGP Graphics card out of its AGP slot then re-inserting it. Then get the drivers.
Cheers, Hope I helped.
Rob