The Winkeyfinder program is another free utility that retrieves product keys from the Windows registry.
Advantages include small program size, no installation required, and additional features such as the ability to change registered user information.
Finds Keys for Operating Systems: Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, Windows 2000, Windows ME, and Windows 98.
Finds Keys for Other Software: Microsoft Office 2013, 2010, 2007, 2003, XP, 2000 SP2, and 97.
Though the program doesn’t state that it supports MS Office 2016, and so, therefore, shouldn’t be expected to, that is one of the only Microsoft-related product keys that Winkeyfinder will not find.