This topic is scaring the willies out of me.
Don't let it do that. Just install XP on your other two machines. I have the same SP1 version (I have a 10 machine site licence) on all seven of my machines. It's actually quite nice on my laptop, as the Acer branded version of XP that came with my laptop used to shut down the USB ports to save power after a few minutes - regardless of whether I was using them or not. Then I'd have to reboot to get audio back. Now I have the standard version installed, I have it configured so it thinks it is a desktop and it never powers down anything.
I wonder if dealers would install XP on those machines for free
Oh, how we laughed! Desktop, maybe - if it was built by a smaller company recently, they may be willing to exchange one OEM version for another. If it's a Dell or something, I doubt it.
Both were OEM versions anyway.
There is a good chance that, even if they were willing, you won't find a manufacturer's install disk of XP for your specific laptop - they make each version specifically for each range of machines with all the needed drivers and laptop management software pre-installed. The "generic" and OEM versions doesn't have that, and works on a wider range of machines. You can then download any extra specific drivers needed from the manufacturer of the laptop.