How can I retrieve the product key for a windows xp intallation disc

It's not on the disc.

Is the version you have the disk for running on a computer?

Maybe I misunderstood. To retrieve it from a working system, use Magical Jelly Bean Keyfinder

On a factory cd or a burned copy of a factory cd the is no key. What there is , is a program that excepts a given number of keys based on the version of the cd. Is it a Dell a Gateway HP? and if so what sp is on it and what version is the cd. Is it retail, OEM...? Finding a key just to install is easy......IE installing using a Dell cd on a HP machine. But you will need to activate and the key you used to install most likely has been used before, so you end up with activation problems. I use the same key over and over on a slip streamed version of xp.....but after installing I use Microsofts key updater and the COA on the machine to make it a legal copy. So you need three things. A working key for the type of cd Microsofts key updater (it is free) A COA sticker to update the key