Here are three utilities which will display your product key:
http://www.magicaljellybean.com/keyfinder.shtml
and: http://www.nirsoft.net/utils/product_cd_key_viewer.html
and RockXP: http://www.majorgeeks.com/download4138.html which has additional
features

Note: Also check the side of your PC case or bottom of the laptop for the
OEM key code. If there is a sticker with the code it will most likely not
match what is displayed by the utilities mentioned above as OEMs such as
Dell use an internal
key code when they build your PC.

in bocca al lupo
JS

If all you bought was the Windows XP Home Edition CD - and you are not
saying that this version is already installed on a system that is currently
working - then you do have a problem.  The CD itself does not contain any
seril or product key numbers.  That (the serial number/product key) is
seperate and in the end - is truly the most important part of your purchase.

If you are saying that the Windows XP Home Edition came with your computer
and that there is no sticker on the computer itself with the product key -
but you have Windows XP Home Edition installed and working already - you can
use something like Belarc Advisor to pull the product key/serial number from
the working install... http://www.belarc.com/

You have two choices, find the packaging or buy another copy of Windows.
Regards   Mike.

First off people who do not speak English well rarely use contractions when
they write. I doubt that you are legit and are simply trying to find a way
to steal a serial number.