PLEASE HELP: "Auto-Protect detected security risk W32.SillyFDC"

Hello. Some weeks ago Norton detected W32.SillyFDC in a USB drive, and it was cleaned (or at least reported like that). After that I made a full scan of the computer just to be sure, nothing was found. The point is that every time the comupter starts up a pop up appears indicating "Auto-Protect detected security risk W32.SillyFDC" and after a minute another one indicating the risk had been removed, but when checking details or history, nothing is there.

 

I have checked other posts and tried everything:

 

- Deleted System Restore Points and emptied all temp folders

- DEleted virus history

- Have no Autorun.ini on c:

- Norton Full scan in Normal and Safe mode found nothing.

- Panda Antivirus online scan found nothing.

- Avast antivirus found nothing in safe mode

- Ran SUPERAntiSpyware Free Edition.

- Followed instructions in  http://www.symantec.com/security_response/writeup.jsp?docid=2006-071111-0646-99&tabid=3

 

After all that, the pop up is still there after start up.

 

My OS is Windows Vista Home Premium. I have no USB drives connected, nobody else uses the computer. Any advice is welcome.