I was having the same problem with the Nvidia 260.99 drivers and Dawn of War 2. The game would freeze, the screen would go black for a few seconds and then the screen would come back. Sometimes the screen would go black and stay black and I'd have to reset. I read that it's the driver crashing.
Since you had to hard reboot without shutdown, I would recommend first running sfc /scannow. Then follow that up with chkdsk /r. You can run them from the command prompt.
Google around and see if there is a driver issue with Splinter Cell. Lastly, certain 4xx / 5xx Fermi cards simply do not work (for some people) with certain motherboards. You can check compatibility on this list:
I was saving this for last but i believe this is the only other solution for me. I ran sfc with no errors and chkdsk is running currently. You think I could get away with installing over the current OS?