About a month ago, something has happened on your system to corrupt the 3D functions. Perhaps it's a problem with the display card itself, but more likely it's a software problem.
To be honest, my own approach to such problems would be to format and reinstall fresh. Such problems can be a nightmare to troubleshoot, and it's often simply easier and quicker to format and start over. But if you want to try, I'd suggest the following:
Download and install the latest version of DirectX
http://www.microsoft.com/downloads/details.aspx?FamilyId=0A9B6820-BFBB-4799-9908-D418CDEAC197&displaylang=en
Download the latest Display driver from www.nvidia.con in preparation.
Uninstall the display driver from Add/Remove Programs (if it has an entry there) and then Uninstall the display card from Device Manager ( Right-click My Computer, and choose Properties > Hardware > Devoce Manager. Right-click the entry for display adaptor and choose uninstall)
Reboot and cancel out of any 'Found New Hardware' dialogue.
Download and install the most recent motherboard chipset drivers from the manufacturer's website.
Install the display driver you downloaded from NVidia by double-clicking it and following instructions.
Uninstall then reinstall any affected games and/or programs.