This may help:
http://support.microsoft.com/support/kb/articles/Q129/2/02.asp

>Hi,
>
>We have three apps written in Visual FoxPro and compiled under VFP 6 SP 5 which are used concurrently for more than 30 users. The apps use one database and its tables, the .EXE files, the .DBC, .DBFs and all the involved files are located on a shared folder in the server. All our user PCs run Win NT Workstation 4.0 and the server Win NT Server 4.0 (SP 6 applied).
>
>Our problem is that some of the apps' shared files (the .EXEs, .DBFs or even the database files) sometimes remain in use on the server by any given user, although they close the apps and windows NT sessions correctly (and they leave their PCs turned off...). There is no apparent reason or pattern to find out what is happening.
>
>All ideas and comments will be appreciated. TIA,