Try removing the first drive, setting the second drive to master(assuming IDE), and then see if the system recognizes the drive. If it does, boot off the distro CD and mount the drive. Iff there is damage to files, you can fix them at that point. You can also get any info off the drive if it is too far gone to reuse as a second drive. Fdisk should give you info on the condition of the partions.
If the drive is SCSI, hit the ctrl (x) or whatever keystrokes are necessary to enter the scsi utilities. Try detecting the drive through the utilities. If found, use the steps above.
If the drive is not detected by either method, I believe the appropriate term may be "toast". If the data is critical, you would need to send the drive to a data recovery service.