Right, let's try something...
1, Click
Start > All Programs > Accessories and right-click
Command Prompt then
Run as Administrator
2, type
sfc /scannow
This will run a system file integrity check which will check to see if your system files are all ok, any changes made will be fixed and a reboot required.
If that reports no issues then you may want to try
Repair Install
It will not affect any user files or programs installed