Windows: LicenseCrawler is a portable and free tool for retrieving serial numbers and product keys from your computer. A simple scan with LicenseCrawler ensures you'll never be left trying to reinstall software without the proper key.
LicenseCrawler doesn't do anything you couldn't do yourself, it just does it much faster and without you actually having to open up your registry editor. The application scans over your Windows registry file, without altering it, and looks for instances of serial numbers, license keys, and other identifying bits of information.
It found a number of licenses on our test system, but it if the application in question doesn't store its product key in the registry—instead in the program or application data folder—LicenseCrawler will miss it.
Have a handy tool for keeping track of and searching out product keys? Lets hear about it in the comments. LicenseCrawler is freeware, Windows only.
LicenseCrawler [via MakeUseOf]