Try the new driver from intel
(you might need to uninstall the old driver first if you get an error message)
and the lates directX update from microsoft
I get excellent video results with these, way above average acording to PCPitstop.
I don't know what kind of games you try to run ...though you've said they were OK before you reinstalled windows. Make a quick check here and see if your hardware meets the requirements.
You could also do a quick restore (about 10 minutes) of your PC with the Symantec restore option, this brings your PC back to the state when you first turned it on for the first time...with all programs and so on...