My iMac (intel Core 2 Duo) won't start up - it has the question mark in a folder icon. I can't find the Apple Snow Leopard disk, so I've started it in Target Disk mode, connected it to my Mac Pro, but it doesn't mount on the Mac Pro even though it appears in System Profiler on the Mac Pro. Both running 10.6.8 Can I force it to mount? I have tried front & back firewire ports and restarted several times to no avail. I'm hoping to repair the iMac disk using Disk Utility or Diskwarrior on the Mac Pro, but need it to mount first. Any ideas? Thanks.