I read with interest Reader to Reader: "Determine Who Has a File Open" (May 2002, http://www.winnetmag.com, InstantDoc ID 24503). However, I have an easier way to determine who has a file open. My method works on Windows NT and Windows 9x.
Select Run from the Start menu, and enter
Winfile is NT's and Win9x's File Manager. You can find the Winfile file in the \%systemroot%\system32 directory. Browse to the file you want (even across a network share). Press Alt+Enter to view the file's properties. Click Open by to determine who has the file open. You can also close connections for the file (either individual or all connections).