If Windows is still running do this: Right-click on My Computer and select
Properties. A properties sheet will open and you will see your product key
there.
If you cannot start Windows, look for the product key among the materials
you received from the computer vendor. It is usually found on an orange
label.
If you cannot find the product key at all: If your copy of XP came
pre-installed on your computer, you must contact the vendor. If you
purchased a retail copy of XP, you will have to contact Microsoft.
Each copy of Windows XP has its own product key. It is illegal to share
product keys.
Mike Mulligan