He's probably got some junk on there from installing too many drivers. He probably left a little nasty bit somewhere that's screwing him over.
First of all, he should know that 3D mark scores are not the main reason to choose 3D drivers. He SHOULD be using 84.66. These are the most compatible. I know because I have a 7600GTS (GS factory clocked at GT speeds). More recent versions have little bugs and display issues that are not present with 84.66. My install CD-ROM came with this version and it seems (for now) to be the best for this card.
Here is where he can download 84.66 However, BEFORE he does that, he needs to clean out the old junk (and there is some, somewhere, that's preventing the new drivers from installing).
I've been careful and never run into this problem, but from what I hear, you need to use either
nVidia Nasty File Remover or
Detonator R.I.P..
Heck, you might have to use both, I don't know for sure (I'm sure others can fill you in).
Also, if he's been monkeying with his drivers so much he can't re-install nVidia drivers, have him run dxdiag and see if it even loads. If it does then he can just worry about drivers. If it returns an error, then he needs to reinstall DirectX as well.