Windows 7 - Video Card stopped working

About a week ago my video card, GeForce 8600GT stopped working, So I switched back to my integrated GeForce 6150LE and then I tried my 8600 again and it mysteriously worked. Then after restarting my computer it stopped working again, The computer and everything loads but nothing comes up on the screen, Any help?

PS: I dont know much about computers but I think it may have something to do with a RUNDLL32.exe virus, My RUNDLL32.exe file looks like a blank page, I heard thats bad, And also sometimes not always my AVG will detect RUNDLL32 and ask me to quarantine but it wont let me quarantine....

This is my Hijack this log I dont know what it is or means but Ive seen people post them, maybe it will help

Logfile of Trend Micro HijackThis v2.0.3 (BETA)
Scan saved at 9:31:19 PM, on 23/02/2010
Platform: Unknown Windows (WinNT 6.01.3504)
MSIE: Internet Explorer v8.00 (8.00.7600.16385)
Boot mode: Normal
Running processes:
C:\Windows\system32\Dwm.exe
C:\Windows\system32\taskhost.exe
C:\Windows\Explorer.EXE
C:\Windows\system32\taskeng.exe
C:\Windows\system32\SearchFilterHost.exe
C:\Program Files\Internet Explorer\iexplore.exe
C:\Program Files\Internet Explorer\iexplore.exe
C:\Program Files\TrendMicro\HiJackThis\HiJackThis.exe
O23 - Service: Agere Modem Call Progress Audio (AgereModemAudio) - LSI Corporation - C:\Program Files\LSI SoftModem\agrsmsvc.exe
O23 - Service: AVG E-mail Scanner (avg9emc) - AVG Technologies CZ, s.r.o. - C:\Program Files\AVG\AVG9\avgemc.exe
O23 - Service: AVG WatchDog (avg9wd) - AVG Technologies CZ, s.r.o. - C:\Program Files\AVG\AVG9\avgwdsvc.exe
O23 - Service: AVG Firewall (avgfws9) - AVG Technologies CZ, s.r.o. - C:\Program Files\AVG\AVG9\avgfws9.exe
O23 - Service: AVG9IDSAgent (AVGIDSAgent) - AVG Technologies CZ, s.r.o. - C:\Program Files\AVG\AVG9\Identity Protection\Agent\Bin\AVGIDSAgent.exe
O23 - Service: nHancer Support (nHancer) - KSE - Korndörfer Software Engineering - C:\Program Files\nHancer\nHancerService.exe
O23 - Service: NVIDIA Display Driver Service (nvsvc) - Unknown owner - (no file)
O23 - Service: NVIDIA Stereoscopic 3D Driver Service (Stereo Service) - NVIDIA Corporation - C:\Program Files\NVIDIA Corporation\3D Vision\nvSCPAPISvr.exe
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