Try running the system file check tool:
* click Start
* click All Programs
, then Accessories
* right click on the Command Prompt
* on the drop down menu which appears, click on the Run as Administrator
* If you haven’t disabled User Account Control (and you shouldn’t!) you will be asked for authorisation. Click the Continue button if you are the administrator or insert the administrator password.
2. Start the System File Checker
* In the Command Prompt window, type: sfc /scannow
* press Enter.
* You’ll see “the system scan will begin”.
The scan may take some time and windows will repair/replace any corrupt or missing files. You will be asked to insert your Vista DVD if it’s needed.
Close the Command Prompt Window when the job is finished.