If, for example, an admin needed to add a dual-boot-to-Ubuntu option to every PC on a floor, he could, through ME, remotely reboot (force power reset if necessary) or power on every machine, have the machines boot to a (remote) OS install disk, run the install, and reboot.
ME allows one to do almost anything remotely to a PC, regardless of what the main processor is doing. That is both useful and frightening.