If you are about to reinstall your computer's operating system, you'll need product keys for all of your software, including Microsoft Office. If you've lost the packaging that has the key on it, you can use a piece of software that will display the key for all of your Microsoft-based programs
Log into your Windows account. Download Magical Jelly Bean Keyfinder from the resource section of this guide. You need to have Microsoft Office already installed.
Double-click the downloaded file, and the Magical Jelly Bean Keyfinder will open. You will see the product keys for all of your Microsoft-based programs, including Office.
Keep the product keys stored in a text document. Do this by highlighting the program titles and the product keys, right-clicking them and clicking "Copy." Open up Wordpad, right-click on the blank document and click "Paste." Save the document and name it "Product Keys."