tool says my video card is not working

[steelman93]

I have been having problems with my 8800GT so I downloaded the tool to scan for artifacts. However, when I try to start the scan it says the video card selected is not used by windows and tells me to go to desktop/properties/settings and enable monitor output. However I am using the card and when I go to device manager it is showing as working fine.

What am I doing wrong?