|I don't know if it will help, but try safe mode. (tap F8 during the boot)|
If all else fails:
Just try a friend's card and install the driver. Then put your original card back in and install it's driver. I think that should work.
FWIW to XP users: When you click on the 'Command Prompt' you are just causing the 'Command prompt' to be displayed. This prompt gives you access to NTVDM.EXE, the 'NT Virtual DOS Manager'.