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I re-installed my Windows 7 installation and I am being asked for the Product Key. But alas, stupid me, I had jotted down the Product ID and not the actual Product Key. Unfortunately, I lost the Windows case where the key is at, so I am wondering if there is a way to retrieve the product key just by using the Product ID?

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Product ID = generic identification of what version/type of Windows you're installing, which is the same for everyone. Product Key = your unique copy of Windows (i.e. the only thing you paid for). – Breakthrough Oct 11 '12 at 12:22
up vote 2 down vote accepted

The product key is stored in the registry, and you can retrieve it from there with tools like KeyFinder. Beware that if you bought the system pre-installed, the distributor most likely used their product key for the initial setup, which won't work with your installation media.

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+1. I've noted on several laptops that the OEM installation key did not work (the one I recovered from the installed copy of Windows), but the one on the actual install media / bottom of the laptop did work. – Breakthrough Oct 11 '12 at 12:24
This depends on the windows version you are using. E.g. installling a shop bought regular windows 7 on a Dell witll ask for a key delivered with that product (or the key from the CoA on the bottom). But a OEM DVD should check the firmware/BIOS for a key and not ask for one. Firmware key and regelar DVD do not work, your two items must match. – Hennes Feb 13 at 14:57

The product ID is completely different from the actual product key, and the latter cannot be derived from the former. The product ID is generated during installation and contains information like the exact Windows version, channel the licence came from (retail, OEM, MSDN etc.), as well as the locale; it is used when getting technical support from Microsoft, it does not prove ownership of a Windows licence.

If you backed up your previous Windows installation, then you should be able to use a utility like Magical Jelly Bean Keyfinder to load the correct registry hive and read the product key. If not, then I'm afraid your only option is to buy a new copy of Windows, since you've lost or erased all traces of your previous licence.

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Your OEM will have affixed the COA with the needed key to the computer. As others have noted, your only real choice is to purchse a new copy of Windows 7 and likely re-install as the key for a retail copy will not work with the OEM install.

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