So what do you do if you need to reinstall the program but you've lost this important, 25-digit installation code? You've probably already tried all the expected 'looking around' but there are a few more things you can try that you may not have known about. Microsoft Office 2021, 2019, 20, like all versions of Office and most other programs you pay for, requires that you enter a unique Product Key during the installation process, proving, to a point, that you own the software.
