There are many programs available for extracting the product key from a Windows XP or Vista installation. The only problem is that they generally require the computer to be functional to run. These programs are useless if the operating system is corrupt and the computer will not boot into Windows. Fortunately, there are other options. This article explains how you can retrieve the product key with just the ntuser.dat file from the machine. You can also download a stand-alone version of my decrypter tool.

While this may not sound very useful to the average user, if you work with computers on a daily basis you have most likely ran into this problem: You have to perform a fresh installation of Windows on a computer with a corrupt operating system, and the product key has been lost. This method makes it easy to find.

The first step is getting the ntuser.dat file from the computer. In most cases the easiest method is to remove the hard drive, and connect it to a working machine.