Windows ME Registry?

I am working on this ME computer and decided the best possible solution to clean up the computer was to wipe the slate clean and start over. I made a backup of everything. And I re-installed. I get to installing Apps and there is an Office 2000 SB ed.
The client can’t find the number.
My Question: How can I find the registry file(s) from my backup and view a certain key to get the pruduct key that was installed?