you havent mentioned which OS you're using or which anti-virus program.(or which virus)
im only guessing but i reckon its within 'system restore' which cant be accessed by some anti-virus.you may need to disable the 'system restore' function to deal with it.
once disabled 'system restore' will lose all previous restore points.
wait for a few more opinions first.(you should of mentioned 'virus' in the title,you may of got more response)