Anyway I can find out the number from a friends HDD as I am currently installing a fresh copy of XP on a spare hard drive before copying his files over to the new drive then the whole lot back to his drive via Acronis.
Have that already on my system, but can only see my COA not the one I need from the other harddrive. Mind you SIW does show two number/letters sets:one is called Windows Product Key and the other is called Windows Default Product Key, both are 5 groups of letters and numbers. So could the second group be what i am looking for?
However - if it was an OEM version, there should be a label stuck on your friends case, and if it was a retail version, it should be on the folder that came with it (ie your friend should still have it).