1) To eliminate a faulty HD try connecting just the Seagate drive, and running HD toolbox to see if it can find the drive now, hardware conflicts are common with SCSI.
2) Make sure you are not using the same device ID as the SCSI controller.
3) Make sure the last devices on the internal and external chains are terminated and all other devices including the SCSI contrroller are unterminated.
Just found this site. thought it might help. :-)
