Mac OS X: Gray screen appears during startup

I'm running OS X 10.4.11 on an Imac G5. It's been running a little slow for the last 6 months at least. Today it froze; this happens occasionally. I had to force it to shutdown by holding the power button. When I started it back up, it never made it past the gray screen (Apple logo with the spinning gear). Multiple force-quits and restarts did not help. I've been following these instructions in an attempt to correct the problem. Sadly, I've had to continue to the second-to-last step after I was unable to repair the harddrive from the installation cd. I am now trying to do an archive and install from the cd but my harddrive does not appear in the 'select a destination' screen (nothing does). Of course I don't want to format the drive and lose the work I've done since my last backup. What are my options?