I haven't done this before, but if you're using Access 2K, does that mean you're also using Win 2K & above server to host this database?
In the Control Panel, go to Administrative Tools and double click on Computer Management. If you're using Active Directory, maybe you can ask your administrator to help with the shares. There is a Sessions folder and you can see who are using which files. You can log them out by right click.
However, I don't know what would happen to the database. It may get corrupted. You should backup before doing anything else.
Also this company has a wealth of products, but this link takes you to the program they have that allows you Total Control over Access on a network. Anywhere from seeing who's logged on to sending warning messages you are about to shut down for maint. etc. Not free but if you need it they have it: