To recover your lost the product key of Windows XP or most versions of Office and have lost the CD case. Here is an small utility
ProduKey which will display the ProductID and the CD-Key of MS-Office, Windows, Exchange Server, and SQL Server installed on your computer.
You can view this information for your current running operating system, or for another operating system/computer - by using command-line options. This utility can be useful if you lost the product key of your Windows/Office, and you want to reinstall it on your computer.
Download ProduKey