But I have been reading that these type trojans keep coming back
Only if you do not remove it properly (basicly it was never gone than) and you do not setup your security properly.
ONLY with the other AV program
If only one av application detects it, it can be a false positive. If this happens contact the av company and ask thme if it is malware or not.
What does that mean
1] Look at the location. It is a temporary file. Can come from any place. 2] What folder exactly?
Its being used by another person or program
Yup, temp files can be in use. Even Avast uses temp files which can not be deleted as long as they are in use. Solution: Reboot and remove them right after windows has loaded, try it in safe mode, or do it from the recovery console.