I put install disk 1 in, restarted and got into the installer, only to be told OS X couldn't mount on the volume (external HDD). I erased the drive, formatted it to Mac OS Extended, Journaled, and it sill didn't work. I tried it with FW400 as well as USB, neither worked. Running 1.83GHz CoreDuo MacBook, using legitimate install disks. I've used the drive before for backups etc, and it works fine. The drive is an ultra ATA 3.5" 7200 RPM drive in an IceCube case.