I bought a 200gb maxtor firewire HD. It had NTFS on it which my mac wouldnt allow me to acces it with. I used disk utility and reformated to unix file system. After it had finished it showed the disk in finder. I then unplugged and put it back in. Now it wont show in finder when I plug it in. It wont show in disk utility either and it causes disk utlity not to be able to see any disks on the computer. It also causes 90% of programs not to run if its plugged and the computer can't shut down or boot up if its plugged in. I have tried it on 2 different macs and they have both done the same thing. My windows computer wont do anything if I plug it in that either.