If you have an Office 365 bundle or Office 2016 / 2019, make sure you can access the MyAccount page so you can reinstall.. If you have Office 2013/2016 make sure you have your 25 character product key. . If you have 2010 or earlier, you need the full 25 character Product Key to activate Office. If need be, you can “extract” the key from ... More @Wikipedia
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