There are many utilities that can help you find a lost Product Key of your Windows installation, but what if the computer is completely dead and unbootable?
Here is a couple of utilities that can get the product key offline, by loading the Software registry hive. This can be especially helpful after you upgrade to Windows 10 and need the Product key of your Windows 7 or Windows 8 installation to activate Windows under the free upgrade or digital entitlement scheme. In such cases you can load the registry hive from the C:\Windows.old\Windows\System32\config directory.
Note that Windows.old folder would automatically deleted by Windows after 28-30 days after upgrading to Windows 10. It’s better you get the Product keys well in advance from the Windows.old directory.
You need to run these utilities as administrator, otherwise you’ll get the error A required privilege is not held by the client or similar, when loading the hive. Before proceeding, note that this article assumes you have a copy of your Software registry hive from your dead Windows installation, perhaps by connecting the drive as slave to another computer or other means. Of course you can load the utilities into Bart’s PE and run it from there.
Keyfinder retrieve product keys from unbootable Windows installations. It also has a community-updated configuration file that retrieves product keys for many other applications.
From the Tools menu, click Load Hive.. and select your offline Windows directory. The directory structure must be intact (Windows\System32\config) as KeyFinder doesn’t allow you to select the SOFTWARE registry hive directly.
That lists your Product keys from the Software registry hive.
ProduKey is a utility from Nirsoft, that displays Product Keys of MS-Office, Windows, Exchange Server, and SQL Server installed on your computer. You can view this information for your current running operating system, or for another operating system/computer – by using command-line options.
Launch ProduKey. From the File menu, click Select Source
Select Load the product keys from external Software Registry hive
Click the Browse button and locate the Software registry hive (of unbootable Windows installation), which is present in the Windows\System32\Config folder. Note that unlike KeyFinder, ProduKey allows you to select the Software registry hive file directly, and you don’t need to have the Windows\System32\Config folder structure.
Click OK. The product keys that are available in the Software registry hive should be listed.
Hope that helps!
About the author
Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and has a vast experience in the ITeS industry — delivering support for Microsoft's consumer products. He has been a Microsoft MVP [2003 to 2012] who contributes to various Windows support forums.