NVIDIA driver help

Ok so my sister has a 8600 gt and just recently she got back into wow. Now her drivers were REALLY old like 150.xx, something like that. We had to update them because wow was not working with her current ones. Well now that we have updated them, she is getting an issue that seem to be not as uncommon with blizzard games as I thought. WOW will stop using the GPU, so GPU usage will be at 0-2% and thus she get like 2FPS. Well I tried older drivers 195.xx and 196.xx and same deal. The consensus is on the interwebz from research I have done is that it is either MOBO related or driver related. A few people also recommended forcing use of the graphics card in the NVIDIA control panel. (I have yet to try that)

So my main question now that I have brought you, the reader, up to speed is, does the new NVIDIA install program wipe the old drivers from the system or are they still on the system. I am wondering if it is an issue with old drivers being on the system. If it does not, where do these drivers like to hide? She is running on 32bit XP still.

Most people would say that it's a good idea to do an "uninstall" and reboot of drivers before you isntall the new ones, personally, I never do. I just install the new ones. Never had an issue like this myself.

Does her mobo have onboard graphics? If so and it's not properly disabled it could be causing conflicts.

I'd fire up DXdiag and veryfiy everything looks kosher. The drivers themselves will be in the Win/sys folder most likely, but who know's what they are named