The "Office Product Activation backup tool" from http://www.opa-backup.de/index_en.php will make a copy of your product activation (license) info, so you can restore it after reformatting the computer and/or re-installing Windows. It can also be used when transferring Office to a new computer, but only if the new computer is nearly identical (same make & model, same version of Windows). THIS STUFF IS REALLY IMPORTANT: Opabackup only works on Microsoft Office 2013 and older versions, NOT version 2016! Opabackup only works on Windows 8.1 and older versions, NOT Windows 10! You must restore the activation data BEFORE you start any Office applications! (In other words, do the opabackup-restore immediately after reinstalling Office, before you try to start Excel, open a Word document, or set up Outlook, etc.) INSTRUCTIONS: 1) Run "opabackup342" before reinstalling Windows, and save the "opa" file somewhere it won't get erased when you reinstall Windows: a USB drive, Dropbox account, etc. 2) After reinstalling Windows and Microsoft Office, use Windows Update to make sure both are up-to-date* -- but don't "activate office" or start any Office apps yet! 3) Run "opabackup342" and restore the "opa" file when prompted. * If you made the backup on a computer that came with Windows 8 and was later upgraded to Windows 8.1, if you reinstall Windows 8 you must upgrade it to Windows 8.1 again before you can use opabackup to restore your Office activation info.