I would try to load the driver in Safe Mode with Networking.
To get there restart the computer and in between the computer logo or BIOS POST screen and Windows (before Windows starts) tap the F8 key.
From the option screen choose Safe Mode with Networking.
This will load only basic drivers but will allow you to go on-line.
Then go back to the nVidia page and try again.
ALSO: One thing that just occurred to me: have you reloaded XP SP2 (if it wasn't included in your re-install)? Many new drivers require SP2.
P.S: No I don't use messengers. Sorry.