ProduKey is a small utility that displays the ProductID and the CD-Key of Microsoft Office (Microsoft Office 2003, Microsoft Office 2007), Windows (Including Windows 7 and Windows Vista), 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.
When the product key is not stored in the Registry (like in volume licenses of Windows 7), ProduKey will display 'Product key was not found' instead of wrong 'BBBBB-BBBBB-BBBBB-BBBBB-BBBBB' key
Tools and Utilities
Product page: here