If you have an OEM version of Office that was preinstalled by your
computer's manufacturer, then you will have to contact your computer's
manufacturer. If you purchased a retail version of Office, then see
http://support.microsoft.com/?kbid=823570 "How to Obtain a New Product
Key for Office Program Setup".

wrote:

I have the original (vs pirated) MS Office and want to
reinstall after I wipe my system. Unfortunately, I lost
the CD case with the product code. What do i do?