ProduKey (32-bit version)
If for some reason you need to reinstall Windows, Office, or other Microsoft applications, and you can't find the original key on a CD, you'll be out of luck. You won't be able to re-install. That is, you won't unless you use ProduKey.
The program is exceedingly simple to use. Run it, and it displays all of your product keys and product IDs for Windows, Microsoft Office applications, Windows Server, and Microsoft SQL Server. There are a variety of command line options, if you'd like to do things such as get product key information from a remote PC, or save the information to a text file.
Note: This software comes in 32-bit and 64-bit versions. This is the 32-bit version. If your 64-bit PC is running 64-bit XP or 64-bit Vista, please download the 64-bit version instead. This review covers v1.35 of the software.