Vista loop of death... stumped!

My HP Pavillion was fine until one day I saw the blue screen of death when trying to boot. The black boot up screens had a messed up sort of tiled blue pixel background, making me think there was an issue with the graphics drivers. Running safe mode worked fine, and the screensaver showed the message "cannot display graphics as there is a video issue" or similar... so today I tried to fix it. I backed up all of my important files and ran the recovery wizard by hitting F11 upon boot, with the intention of starting fresh with Vista.

I followed the wizard's steps and chose not to make a system snapshot/back up, as had saved everything I wanted and feared making another back up on the same HDD may mess things up.

When it had finished it said "now loading Vista for the first time", though the messed up blue pixel background was still showing on top of the black background. After a few minutes, I got the BSOD again, and back in the restart loop.

Going into safe mode now gives me the message "start Windows normally so that Vista can finish installing", and then it restarts, and of course starting Windows normally results in the BSOD.

I've tried a couple of memory/disk tests in the BIOS screen but nothing worked. Annoyingly, if I had chosen to make a snapshot back up I could probably at least go back into safe mode.

I'm totally stumped on what to do here. I do have a way of using the command prompt if that would help at all. I've read up on things like re-seating the BIOS battery, or typing a particular code into DOS to reset the BIOS, but am a little worried that's going to make matters even worse.

Would anyone have any suggestions? I'd really appreciate them. Thank you.