Are you sure Tiger didn't just reset your preferences so hard drives are not displayed on the desktop?
Does the drive appear in the Finder window's sidebar?
Is it internal or Firewire?
If it's external, try unplugging it, restarting the machine, and then plugging it in again.
Try repairing the drive with Disk Utility.
Select the drive in Disk Utility and click the "Mount" button.
Chris