Finding Exchange CD-key (I own it)

My company just bought another smaller company that sent us 3 PC’s with Windows 2000 and Exchange 2000. Well, we want to use this Exchange
server and I would rather reinstall everything then keep it as it is.

The IT man for the last company is gone and we don’t have the CDkeys for the software. I ran a program to get the Windows CD-key, but is their a way I can get the Exchange CD-key?