Reinstalling WinXP without having to Re-Activate

If you reinstall Windows XP, you normally have to reactivate it, but there's a workaround:

Windows XP maintains the activation information in the file Wpa.dbl, which you'll find in the Windows\System32 folder. 

After you activate, and any time you add hardware to your system that may cause reactivation, back up the file to another disk. 

If you need to reinstall Windows XP for any reason, go through the installation routine, then copy the latest version of Wpa.dbl to the Windows\system32 folder.