How can I tell which process has file X open?

A. You can view files that a user accesses over the network with the Net File command

D:\&gt;net file<br><br>
ID         Path                                    User name            # Locks<br><br>
-------------------------------------------------------------------------------<br>
51         G:\www.ntfaq.com                        ADMINISTRATOR         0<br>
The command completed successfully.

You can’t use this command to access information about files that local processes open. Two programs, NTHandle (a command-line tool) and HandleEx (a GUI version), let you view which process has file X open. Both programs are available from http://www.sysinternals.com.

Click here to view image
Example of HandleEx in action.