From Satel Enterprises:
Have multiple users working on the same files and documents in the same folder? Easily setup File Cabinet on all the computers and you will start benefiting from the great features of this free software. When you check out a file to work on it, the file automatically becomes read only and specifies what computer/user has checked the file out on what date. You can also check the log of a certain Cabinet to see all the check in/out activity done by all users. Just make sure that users have read/write permissions on the Cabinet folder.