Actually I have read legal opinions that the EULA on MS oem software states the OS in essence is being rented by you for use on that particular machine. I also read that the machine "owns" the software, not you. You therefore legally can't put it on another machine. This raises the question of when a machine is no longer the same machine. If I replace the mobo, cpu, memory, hard drive, cdrom but keep the modem is it the same machine? What if I replace the case?
Anyway, in the past oem "recovery style disks" only worked on the machines they were sold with, or very similiar models. The recovery cd reads a bios code or other hardware built in identifier to enable it to install. Dell used to include standard windows 98-me, etc disks that could be installed on any machine. The dell Windows XP disks don't look like the standard windows disks and are labeled "recovery software" so unless anyone has tried it and finds it will work on another machine I would assume not. MS are not dummies. They wouldn't go thru this whole Activation thing only to allow the oem disks, which don't need activation to work on any machine.