Restart in Safe mode.
Goto the Control panel and then into Device manager.
click the topic "Video adaptors" and see if you have more than one videoboard listed there.
Remove the ones that are no longer present.
Remove ALL items if they are double ore even moretimes listed. (YES, ALL, until ALL that items are gone.)
You can do a nice cleanup of your system by doing it with all of the topics in the Devicemanager.
There is ONE exeption!!
The topic, System devices, or as to say the one with that blue monitorscreen should be left alone. (I am Dutch and does not know the exact english word for that)
There ARE double entries in there who are ment to be.
Restart the system and Windows will reinstall them properly.