Open Control Panel\All Control Panel Items\System\Advanced System Settings\Advance\Settings under Performance:
Under the Visual Effects tab scroll down to Use drop shadows for icon labels on the desktop and uncheck the box against it.Click OK/Apply.
If the above doesn't help:
Update your Graphic card driver.Visit the website of the graphic card manufacturer to download and install the latest compatible driver.
If the above doesn't help then:
I shall suggest you to test your desktop first by connecting it with a different monitor.If you don't experience the problem with another monitor then definitely it's a problem with your mo