What is the make and model card? If you are running an ATI model you can use the overdrive tab in the advanced settings if you are running the Catalyst Control Center. ATI cards as well as some NVidia models come with a
LM63 monitoring chip on the card itself. Without that there are no programs apparently that can actually monitor the temps there. One place to see if your card is equipped with this is at: http://www.techpowerup.com/articles/overclocking/vidcard/94 But this is mainly concerned with ATI models there.
SpeedFan may help you out there. First you click on the "configure" button found on the Readings tab. Then look the Local and Remote temps provided by the bus value. You select those two items on the Charts tab. You can download SpeedFan free at: http://www.majorgeeks.com/download337.html or from the download link on the home page. http://www.almico.com/speedfan.php
Note on the Charts tab the last item there is usually the hard drive temp reading. The two right above it are for the video card. When you check those two items you will then see two different colored bars on the screen. Look in the top portion then to follow those two on the temp chart will displays the temps seen during a certain time period.
