WinXP Serial Numbers/Registration

I recently migrated a single workstation and server network to a 4 workstation network with a Win2000 SBS network. I needed to get things up and running quickly, so I used the same copy of WinXP Pro on each of the workstations. Now that the madness of moving the office and setting up the new network and getting all the other software packages up and running, I have purchased the additional licenses for WinXP Pro for the new workstations. Is there a way to update the license/registration for these new workstations without having to completely reinstall the new WinXP Pro copies onto the workstations?