video card 6800 problem

I have a XPS400/9150. My Dell warranty expired in January. For several months, maybe since I've had the system, I've had problems while playing any video and TV no matter what software player I used, I prefer Video Lan. The system would start to stutter after a while of video and TV play . After months of re-formatting, replacing thermal paste on cpu heat sink, and trying various other remedies, I finally found the problem. The video card. I downloaded Riva Tuner and PC Wizard 2007. Riva Tuner allowed me to adjust the fan speed on the video card to 100% and PCwizard2007 gave me a constant Graphics card temp monitor. I realized that when my 6800 temp reached an idle 68 degrees Celsius the problems would begin. I then replaced the thermal paste on the 6800. Increasing the fan speed on the card to a constant 100% helped somewhat but didn't fix the problem. What should I do since my warranty has expired? Are Dell 6800's lifetime warranty cards? From what I can tell, it seems that 6800's have been notorious for heat related problems.