Some IDE to firewire adaptors found in older firewire cases have the same limitations that older IDE chipsets have, they don't have the 48 bit LBA addressing needed to support drives larger than 128 GB. You have three choices, in order of increasing cost: 1) Buy the HD driver software from Intech (http://www.speedtools.com/ATA6.html) and install your disk internally to your machine. $25 2) Buy a new firewire case. $50+ 3) Buy an IDE PCI card and install your disk internally to your machine. ~$75 (http://www.macsales.com) Note that the software solution has limitations that may or may not matter to you depending on how you want to use the drive. Phil