O LockHunter é um unlocker de arquivos infalível.
It is a tool to delete files blocked by something you do not know. LockHunter is useful for fighting against malware, and other programs that are blocking files without a reason. Unlike other similar tools it deletes files into the recycle bin so you may restore them if deleted by mistake.
Principais recursos
Shows processes locking a file or folder
Allows to unlock, delete, copy or rename a locked file
Allows to kill locking process
Allows to remove locking processes from hard drive
Integrates in to Explorer menu
It deletes files into the recycle bin, so you may restore them if deleted by mistake
Supports both 32 and 64bit Windows
quanto à sua pergunta:
Is there a way to find who / what's using the file?
LockHunter é freeware.