Mazahir,
I just checked up an thread on http://www.foxite.com/archives/vfp8_error_no_171_0000029324.htm
The same error but with VFP8 and Win98. I don't know what happens but you can try to log as an Administrator (as you do) uninstall your application, delete your application folded, delete all VFP6*.* files on that computer, delete all foxuser.* files also and then reinstall your application.
I have no idea what you can do more.