I reviewed two different product key utilities, with the purpose of keeping a backup of all my product keys in case I ever need to reinstall my applications. The programs I tried were Product Key Finder and MSKeyViewerPlus.
I tried MSKeyViewerPlus and immediately liked it. It separated those applications that required keys and those that did not (free). With a single click I was able to expand the window to view all the key information, and with another click I had them all copied to the clipboard. MSKeyViewerPlus was created by a guy named Todd (couldn't find his last name) and he makes it available off of his family website for free.
The other program I tried, Product Key Finder lists all your registered programs on one screen and does not provide an alternate screen with your other programs. On the plus side, it offers different output options to save your records including XML, Access, CSV and Tab Delimited. These programs are not that complex, so there's not much more to it. Product Key Finder costs $30 and a purchase is required to really use it, though the site claims 15 free trial. In addition to the $30 fee, what I didn't like about Product Key Finder is that you cannot uninstall it if you do not let the program have access to the Internet.
Having to allow Internet access to uninstall any program is not acceptable under any circumstances. Product Key Finder did not give me any information as to what data was being sent while accessing the Internet. And even if it showed me some data, I have no way of ensuring that something else is not being sent. So whether using Product Key Finder or another product, whether I pay $30 or I get it for free, there are very few programs that I could recommend that requires Internet access to uninstall. For that matter, I would also be cautious of programs requiring Internet access for installation.
So there you have it. If you want to make a backup of your product keys, checkout Todd's MSKeyViewerPlus. While you're on his site, Todd offers some other free utilities that may be of interest too.