I would venture to say it's either the grapics card (as you suspect) or a virus. When you re-installed Windows did you format your hard drive and start anew or did you just erase Windows and re-installed it? Most of the time a format and re-install will get rid of a virus even when your anti-virus program can't. The fastest way to check out a video card is the switch it with another if you have one available. If not, you might pull out the card and take it to your local computer repair shop, or maybe the Geek Squad at BestBuy will check it for you.
However, it would be more efficient to check by switching with another card in your computer in case there's is something else in your system causing the problem and not the video card.
I've had my PC for about 4 months now with no problems...sorta.
I have a Nvidia Graphics card (I believe the 7200? one of the newest better models) as well as gforce motherboard. The monitor I use is an Apple 23" cinema display and 2gigs of Ram.
The only thing I basically use it for is playing World of Warcraft and it has run great with full settings, but I did notice about a month ago that sometimes during playing it would "lock up" for about 5 seconds then I would hear a "click" from in my PC then it would go back to normal play.
I also recently started getting small colored dots on my start-up screens, like around the windows logo and also rows of letters on the DOS screen are now pink. It seemed like this was getting worse as it went on (more dots would appear etc.)
Now the major problem:
I got home from work last night and went to wake up my PC and I couldn't open any programs, so I shut down and tried to restart but no matter what mode I tried starting in (safe etc.) it would auto-restart again at the windows loading screen. So I went ahead and re-installed windows, reinstalled my drivers, reinstalled WoW and now I'm able to load Windows fine but I am still getting the colored dots and letters upon start up. I also noticed these colored dots/patches now on my WoW loading screen and one time I even had a large bar of all sorts of colors (didn't look good) behind my character on my character select screen. I also can't stay logged into WoW for more than 10 seconds now as well, if that helps figure this out at all.
Is this a sign of a faulty graphics card? Is it just dusty and needs to be cleaned? My PC has a great cooling system, but maybe this is letting too much dust in from all the fans and vents? Please help this is very frustrating.