You cannot legally load your version of XP Home on a second computer. The license you have is valid for one and only one computer unless you have an Enterprise version which is unlikely, and almost impossible for a home version. Enterprise versions are sold to companies that run more than 250 computers and is a bulk license subscription, and corporate entities would run XP Pro, not XP Home as XP Home doesn't have anywhere near the security abilities of XP Pro.
By the way, you do not "own" the license - Microsoft retains ownership.
Try logging in as "admin" or "administrator" without using a password. That might work if you never set an administrator password and left the default account open.
Do you have the original Microsoft Windows XP Pro Installation disk for the computer along with the "key" that came with it? (or a complete restore disk provided by the computer manufacturer?).
If you do not, the computer manufacturer may be willing to provide a copy (usually for a fee, but much lower than the price of a new install version) for the one registered to the computer.
If you do have it, or get it, you may be able to format the hard drive and do a fresh installation, allowing you to reset the admin account, but you will still need the valid "key".
By the way, XP, either Home or Pro requires validation with Microsoft within the first thirty times the system is booted or it will shut down and deny further access, so you need the valid key that came with the installation disk. They will recognize a previous installation on a different computer.
The upgrade version of XP Home cannot be used to "upgrade" a version of XP Pro to XP Home. It would require a full install version to do a fresh install after the disk was formatted if that's what you really wanted to do.
Edited by Enthusiast, 05 January 2006 - 12:02 PM.