Product Key

I used jelly beans to find my Windows Xp prof 2003 product key. I wanted to use the program to find if the key they find from the system matches with the one on the Windows Tag pasted to the bottom of the laptop. AND…the product key that i discovered using Jelly Beans DOES NOT match the one on the tag at the bottom of my laptop. Am i doing something wrong here?
My real problem is i dont have the product key of my Office XP hence need to find the Product key in case something happens to my laptop and i need to reinstall.