No, you can't do that. You can install your WindowsXP to a second PC using the install disk ONLY if the first PC is no longer being used. Depending upon what version of WindowsXP you have, you might not even be able to that. (OEM version versus retail.)
Your license is only good for one computer. It would be illegal to install it on two computers. Not to mention, Microsoft wouldn't allow you to register it, so it wouldn't work.
Best bet is to purchase a new copy of Windows for the second machine. Preferably Windows 7. It's a much better OS than WinXP.
Good luck!