Hi,
Sorry for the inconvinience.
Could you please tell us when did this issue begin to occur?
Please update or reinstall your graphic driver by going to Device Manager->expand Display adapters->right click on your display card and either update the driver software or uninstall the driver. Restart the computer, driver will be installed
automatically.
In case it is due conflict with certain third party software\services, let us prepare clean boot to troubleshoot:
Clean Boot prevents software conflicts by preventing the startup items and non Microsoft services from loading. This way you can safely follow the process of elimination to check which application is causing this behavior.
Refer:
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
http://support.microsoft.com/kb/929135
Note: Ensure that you put your computer back to normal startup mode after completing the troubleshooting steps. Steps are available in the article given above.
Regards,
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