Have you completely uninstalled and reinstalled the nvidia driver? If you dont know how to do that ill give instructions below
Start > Right click Computer > Manage
Click the little arrow next to "Display drivers"
Right click (in your case) NVIDIA GeForce 8800GT(Microsoft Corporation WDDM V1.1) > Properties
Then click on the tab "Driver"
Then Click "Uninstall"
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Make sure you have a new driver ready for your card. also make sure the driver IS NOT a beta.
Once downloaded, just Right Click the Exe and click "Run as Administrator"
Follow the prompts, then once installed restart your machine. Let me know if this helps