The file you mention is component to your nVidia video solution - leave it alone.
My suggestion would first be to go to Add/Remove prgrams, and get rid of anything you don't use, including installed Windows components which are irrelevant to your customary usage.
Then, if you're running WinME or later,
Disable/Re-enable System Restore, which will clear your stored restore points, then
Reduce the space used by System Restore.
Next, delete
All Files in
C:\Documents and Settings\Administrator\Local Settings\Temporary Internet Files ,
C:\Documents and Settings\(for each user name)
\Local Settings\Temp ,
C:\Documents and Settings\(for each user name)
\Local Settings\Temporary Internet Files ,
and
C:\WINDOWS\Temp
(in all instances, delete just the files in the parent and daughter folders, do not delete the parent or daughter folders themselves).
Search through your My Documents, My Pictures, My Music, and My Received Files folders, under each user name, and delete everything you know you've archived elsewhere, archive anything else you want to keep, and empty the folders.
While CCleaner, as recommended by Ticomaya, is excellent, in your situation I would recommend instead
CleanUp4! ; its very small (about 332K), very easy to use, and can't screw anything up unless you go out of your way to adjust its hidden settings.
Empty your Recycle bin, boot into safe mode, defragment, reboot once more, and with nothing else running, see what happens when you try Disk Cleanup.