As a DBA you land in situation where you need to find which process is using a File on the disk,
For Eg:- Your Tape backup process may be holding a old backup from Archiving or using it of Restore or a Application process may be holfing a File used in ETL making the ETL process to fail.
The best tool to find which WIN process is holding Flat files is "Process Explorer"
The exe is found in Windows Resource tool kit and does not need any install, all you need to do is copy the exe and start using it.
I have been using this for nearly 10 years now and works perfect every time. All you need to do is enter the file name are part of filename in the search box and you will get all the information you require. You can Also Kill the WIN Process or process tree using Process Explorer.