You cannot upgrade from XP to XP, so you cannot use your present disk to validate the upgrade version.
However...
The XP validation is to stop multiple copies being run off. They expect people to re-install their OS on other machines at regular intervals. So, as long as it has been over a couple of months, you can install your current copy on a new machine. And no, that does not mean that the other machine will then fail to update, validation is not cross-checked after installation.....