The real question is why it remains in the windows\temp_avast_ sub folder.
The avast is where avast scans files, on successful completion of the scan avast should remove the contents of the avast folder.
One possible issue is another security based program, locking that file and not allowing avast to remove after completing the scan. Do you have any other security based applications, e.g. anti-spy/malware programs.
Have (or did) you another Anti-Virus installed in this system, if so what was it and how did you get rid of it ?
