Find your Windows Product Key on a Running Machine.

• Magical Jelly Bean Keyfinder: This is probably the best tool for this task. In addition to finding and identifying product keys for Windows 95/98/ME/NT/2000/XP, it can also uncover product keys for installed versions of Microsoft Office.
• Windows Key Finders: This is actually a group of tools that can be used for unearthing product keys for different versions of Windows.
• Belarc Advisor: This free utility builds a detailed profile of your installed software and hardware. (As suggested in the discussion thread byShadyHouse).

Find a lost Windows product key