How to change product key from the XP on my used comp

[Mariposa]

I recently just bought a used comp. from a friend and the copy of Windows XP
is not valid. I recently had a friend who has a VLK borrow me their disc and
the key. How do I go about changing the product key on comp to the new one

 

[Anteaus]

You cannot apply a VLK key to an OEM or retail copy. You would have to
reinstall using VLK media. Even then, if it's a widely-pirated (and therefore
blacklisted) VLK key you will not be able to access Windows Update, etc.
using it.

 

[Carey Frisch [MVP]]

You cannot use a VLK that does not belong to you. Your friend
cannot give you a legitimate VLK.

In order to resolve your non-genuine licensing issue, please visit:
www.microsoft.com/genuine and click on "Validate Windows".
When validation fails, click on the "Get Genuine" button which will
provide information on how to acquire a WGA Kit.