Wow, I'm surprised you all don't know this.
You can install the same copy of Windows on TWO separate machines, and it is 100% LEGAL...PROVIDED that both machines are never in use at the same time. I believe that MS understands this, and, as such, will allow you to install WinXP on both a desktop machine and a Laptop machine, since presumably, you will use your laptop while away from your desktop, and vice versa. I KNOW that this is legal, and I'm 95% sure that I read that MS will allow simultaneous installs of one license, provided one is on a desktop, and the other on a laptop machine.
Jman