Here’s a situation to be avoided—for one reason or the other you have to reinstall the Windows operating system but you discover that you don’t know the product key. To avoid this predicament, retrieve the key now, print it out and put it somewhere safe.
There are numerous programs that will retrieve the Windows product key but many will not work on 64-bit systems. Some favorites like Belarc Advisor and System Information for Windows are very useful for providing all sorts of information but are overkill if all you want is the Windows key.
Produkey from Nirsoft is a portable utility that requires no installation and can be run from a USB key. It works in all current versions of Windows including Windows 8. It does have the restriction that it does not work for Microsoft volume licenses in Windows 7 and 8 or certain OEM keys. There are both 32- and 64-bit versions. It also provides the product key for Microsoft Office. The description and download are at this link. The download link is near the bottom of the page.
Windows Product Key Viewer
For a quick and portable little program that works in 32 and 64-bit versions of Windows XP, Vista, 7, and 8, try Windows Product Key Viewer from RJL Software. It works from a USB key and is only 509 KB. It is free but it does put up a little flash screen for a second or two when you close the application. It only does one thing but it’s quick and easy to use. It has an option to print the key or save it to a text file. Requires administrator privileges in Windows Vista/7/8.
Magical Jelly Bean Keyfinder
Another little portable program to consider is Magical Jelly Bean Keyfinder. This program has been around for years but it has been updated to handle Windows 8 and 64-bits. It's another application that puts up a splash screen when you close it. Added later: This is another utility that the developer is now apparently bundling with other programs. (See comment by Chi-stan below.) The download on the developer's site is labeled as an "installer". Since this keyfinder is a portable program, no installer is needed. Instead of downloading from the developer's site, look for the ZIP file at locations like MajorGeeks. Do not download the file labeled "installer".
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