NOD32 has been reported to miss stuff, whereas KAV has found it, KAV might use more resources, but it scans more thoroughly. Also the fact that KAV is free adds to the advantage. .
Lol too bad i didn't read this earlier because i think Avast would have solved your problem. It runs before windows boots so anything that can't be deleted becasue it is in use can be because it isn't : P