And people say ATI has problems with drivers lol.
Anyway, first thing to try is starting with downloading the most recent WHQL driver from Nvidia's website, as well as Driver Sweeper (from Guru3D)
1) Uninstall all Nvidia/PhysX video drivers from your Add/Remove Programs list
2) Run Driver Sweeper and remove all reminants of the drivers as well (if you have an Nvidia chipset motherboard, be careful to only remove video drivers)
4) Install drivers
Try these steps and report back