This may be an isolated case, but these drivers screwed me up bad. I recently built a new rig that I will list below, keeping my old card until xmas.
I originally thought that I had a bad mobo or memory until I booted into safe mode and found that it was my agp440.sys file was hanging. The machine would go as far as the Windows XP load screen and that was it. I backed the driver out and I was back in.
Abit IC7-G
2x 256mb Muschkin 3500 black
WD 10,000 RPM Sata
P4 2.6
Everything else is in the sig below
Microsoft has a bad fix on record for fising the issue, but there seam to be many causes for it. Disabling AGP support or something unacceptable.