How to Find Your Product Keys for Windows and Microsoft Office

You just replaced your PC's hard drive, but now you have to reinstall and reactivate Windows or Office on your new system. Can you do it without the product keys for your software? There are some tricks, but you'll have to use them while your current hard drive is still alive and well.

With Windows 10 and 11, the OS should automatically activate as the license is usually digital and doesn't require a product key. But with older versions of Windows and with Microsoft Office, a product key is required. For the latter, you can use a third-party utility to display the keys on your PC before a crash occurs, save those key numbers, and squirrel them away just in case.

First, let's go through the scenarios in which you would or would not need a product key to reinstall and reactivate certain Microsoft software. Even though Windows 10 and 11 typically don’t require a product key, there are exceptions, as described in this Microsoft support document. If you purchased Windows 10 or 11 from a retail store or on a new device as opposed to upgrading from a previous version, then you have a product key and would need that to reactivate the OS.

Windows 8.1 and Windows 7 both require a product key for activation, as detailed in another Microsoft support document.

And what of Microsoft Office? If you have a subscription to Office 365, you don't need a product key. You just install Office 365 on your new hard drive as part of your subscription (though you might have to contact Microsoft to activate it). If you have a digital or physical copy of any version of Office, then you’re given a product key that would need to be entered.

In general, having the product keys for your Microsoft products is a good idea. The easiest way to grab those product keys is from the product box, or in the case of Windows, from a sticker on your PC itself. But if those avenues aren't accessible, here are three products that can reveal your product keys so you can keep them handy.

Belarc Advisor

The free and robust Belarc Advisor provides a wealth of information about your PC and software. You'll find details on the different hardware components that make up your computer, information on attached accessories such as printers and your monitor, and a list of networked devices. For our purposes, Belarc displays the software installed on your PC along with their products keys. You'll see the keys for Windows and Office as well as non-Microsoft software.

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Magical Jelly Bean Keyfinder

Another free utility, Magical Jelly Bean Keyfinder serves up product keys for Windows and Office 2010 (it doesn't support more recent versions of Office) as well as non-Microsoft software. You can print the product key information or save it as a text file or a CSV file. A more advanced program called Recover Keys offers additional options for $29.99, but Jelly Bean Keyfinder should suffice if you just need the product keys for Windows and Office 2010.

Product Key Scanner

NirSoft’s free Product Key Scanner will scan your installed versions of Windows, Office, and other programs via the BIOS, the Registry, or a Registry file saved on an external drive. The software works with any version of Windows from XP to Windows 10, both 32-bit and 64-bit flavors.