In OS9: If the startup volume does not appear on the desktop run the Disk First Aid utility from you OS install CD. Insert the CD and reboot the computer while holding the C key.
Disk First Aid sees the drive if the hard disk is functioning and allow you to verify and repair the drive.

In OSX: Boot the computer from your install disk inserting the disk and rebooting holding the C key.

Run Disk Utility and "Repair Disk" on the System drive.