About a month ago I got a virus on my PC (running Vista), after running as many antivirus programs as I could get I couldn't get rid of it. I eventually read about autorun viruses and killed the autorun files on my external backup drive. Seemed to clear the problem for a while but it came back. Decided to reformat drive and install Win7. No problems for a couple of weeks but virus came back and now nothing will find it. Symptoms: On load there are several strings of coloured pixels around the screen which come and go. The screen will flash (on Vista) or close and restart (Win7) as graphics is recovered. The screen will distort and become very blurred. Eventually the screen shuts down completely but not the computer. The screen freezes and mouse stops working. I did consider that the whole problem was graphics based but the antivirus software shuts off (happened with Norton 360 on Vista and Microsoft SE on Win7) Malwarebytes scan in safe mode finds nothing. I don't know where to go from here - am considering buying a new pc, but if I don't know how the virus is getting in will it infect that? Sorry to ramble - any help would be greatly appreciated!