In most cases this is due to an improper display driver.
To check your driver, click the 'Start' button, type 'Device Manager', and click on it to run. Expand the 'Display Adapaters' node (by clicking the plus sign to the left of it). The make and model of your adpater will appear. Double-click it to get the properties dialog. In the dialog, select the 'Driver' tab. Beside 'Digital Signer:' you should see 'Microsoft Windows ...'.
If you see 'Not digitally signed', you do not have a valid driver. In this case, go to the manufacturer's website and download and install a valid driver.
If your driver is properly signed, check the 'Driver Date:' to see if it's more than a couple of years old and if it is, try 'Update Driver'.