Probably just a HD and optical drive I assume?
Disconnect each one individually until it doesn't hang. This will tell you which drive is the problem drive.
Once you know, try a different cable on the drive. If that doesn't do it, switch the problem drive to a different channel. For example IDE 1 to IDE 2.
This will narrow it down so you'll know which component is the culprit.
Edit: If it looks as though the motherboard is the problem child, reset the CMOS before declaring it dead.