How to change the Office or Outlook Product Key
How can I find out which license I’ve used for which computer and how can I change the key if needed?
While you could simply try one of your Product/License Keys and see if it gets accepted, it’s not a very sophisticated approach.
The correct way to determine or change the product key depends on your version of Office or Outlook. However, you do not need to completely reinstall Office for either version.
Note: Office 365 installations don’t require a license key as they activate automatically when you log on to Office with your Microsoft Account.
Determine the Product Key with a 3rd party tool
Determining the used Product Key when using Office 2007 or previous isn’t directly supported by Microsoft. However, you can use a little program called Magic Jelly Bean Keyfinder to find out your used Product Key. Simply install and run the application to find out the Product Key.
Another free application that can be used is Belarc Advisor. This application will perform a more comprehensive scan of your computer and generate a report for it, which also contains the license keys for your multiple installed applications. If you are in a large enterprise network, you may need to disconnect from the network because it also tries to build a network map that could cause the application to hang at the Check this computer’s local network phase.