Ever wondered which program has a particular file or directory open? Now you can find out. Process Explorer shows you information about which handles and DLLs processes have opened or loaded.
http://www.sysinternals.com/ntw2k/fr.../procexp.shtml
Win9x/Me
http://www.sysinternals.com/files/procexp9x.zip
WinNT/2K/XP
http://www.sysinternals.com/files/procexpnt.zip