This happens to everyone at some point of time or other and is most likely caused by some application or third party utility overwriting your drivers files (or if you do not have had a right video driver to begin with). To verify exactly what gets loaded, follow these steps. Open registry by going to START-RUN and entering regedit. Navigate to :
HKEY_LOCAL_MACHINE\\hardware\\DeviceMap\\Video . In this value of Device\\Video0 points to a registry key that has the location of the video driver that Windows is configured to load. for example: HKEY_LOCAL_MACHINE\\System\\CurrentControlSet\\Services\\ videodriver \\Device0 . Navigate to this key. Check value of "InstalledDisplayDrivers" . Its value indicates whether driver was loaded or not. If the setting shows another registry location, a third-party driver may be getting loaded. Check out Microsoft Knowledgebase article for more details
