I can't verify if there is a virus that out there that attacks graphic cards, but it wouldn't surprise me. But the fact that it runs well in only Aero mode makes it sound more like a windows or graphics driver problem then a virus. Or a misconfiguration of sorts.
You could try the following:
Open the laptop and run the PC, make sure the cooling fan is working on the graphics card.
Try unplugging and re-inserting the card and see if this has any effect.
Verify that the drivers are up to date, for both windows and the graphics card. You may want to reinstall the graphic card drivers.
You can go to this page and d/l and run the symantec online scan, it's free, it will d/l a AV scan engine to your PC and run. Click on "Continue to Symantec Security Scan" and follow the directions. You must be running IE to use this service. http://security.symantec.com/sscv6/WelcomePage.asp