Hi Bruce,
Sorry, doesn't compute: Windows won't let you rename a file with the name
of an already existing file (in the same folder).
If you have overwritten the file (saved a file from Word with the name of
an already existing file, and answered "Yes" when asked "The file XY
already exists. Do you want to overwrite the existing file?"), then the
original file is gone.
You might have luck with specialized software that sometimes can retrieve
overwritten or deleted files. The less you have worked on the computer in
the meantime, the greater the chance that you can retrieve the file.
Look at
http://www.snapfiles.com/get/restoration.html, or google "undelete"
for similar tools.
:-( Klaus