All 3 systems have their own individual HDD, They are all the same model (160 Gb SATA) I don't have the specific model# because I'm not near the machines right now. Sorry for the confusion...no, the systems will not boot by removable media. A bootable cd/dvd is recognized and will run, however the hard disks will not boot because they're not being recognized. I have tried swapping SATA cables and ports, I've swapped hard drives from one machine to the other and the result is the same. I've contacted HP support and they've only offered me the suggestions i've already tried. Their conclusion is that the SATA controller has gone bad on all 3 boards. This is obviously not true because the optical drive is recognized on all 3 machines and these are SATA drives as well.