It may be hardware, but first roll back the video driver and see if that helps
Go start > run
Type in :
devmgmt.mscThis will open device manager
Locate your video card
Right click and select properties
Select the driver tab
Select roll back driver
Download
Speedfan and install it.
Once it's installed, run the program and post here the information it shows.
The information I want you to post is the stuff that is circled in the example picture I have attached.
If you are running on a vista machine, please go to where you installed the program and run the program as administrator.
(this is a screenshot from a vista machine)