I have covered couple of these software before but I am compiling these in single post. In case you lost your Microsoft product key but you have the product installed at other PC, then here are some really good programs that can digg deep in Windows and bring back Windows XP, Vista, Win7 keys or Microsoft Office keys really easy for you. You can resurface Windows XP hidden keys and passwords or trace Windows Vista and Windows 7 serial keys. Download Windows Keys Finder utilities. We have CD Key seizer, RockXP, and WinGuggle here.