Recover the previous version of a file

I have a user that works from his PC at home and a PC here at work. The work PC is a stand alone box. Here is the problem. He took an important file home to work on it, renamed it, and when he brought it back in he copied it back to his PC overwriting another file on the PC, one he shouldn’t have written over. He now has lost an important file that he needs back.

This file is an Excel 2000 file (.xls) on a Windows 98SE machine. Is ther anyway to recover the file that was wrote over or a utility (free) that can get this file back?

Thanks,
Mike Moegling