Internal iMac hard drive keeps trying to power down without my consent

Question

How do you stop an internal hard drive from shutting down when you didn't ask it to?
Background:
I use Missing Sync for Palm to sync my Palm handheld with my iMac. My Palm has a SD card slot it in and the sync software came with a program that allows me to mount the
SD card as an external drive on my iMac. From there, I can add podcasts, music or whatever I want directly to the card. I have used this software since March with no problems.
Also, when you put my computer to sleep or shut it down, there is a click and then the internal hard drive shuts down.
Last night, I activated the program to mount the SD card to my iMac and instead of it mounting, the iMac's internal hard drive started trying to shut down.
I have used this program many, many times to mount the SD card to my iMac with absolutely no problem. It was weird this time because I kept hearing that clicking noise. The computer became extremely sluggish. To me, it appeared that the internal hard drive was trying to shut down. After about 4-5 clicks, it succeeded and the computer froze.
Since that time, shortly after you turn the iMac on, you hear that clicking noise trying to power down the hard drive. Sometimes, it just takes a few clicks and the hard drive shuts off. Sometimes the computer will boot all the way up, I can log in and launch a program before it shuts off and the computer freezes. While I can't check the drive with First Aid or Diskwarrior because it shuts off before I can scan it, I assume the data and the drive are ok because I have been able to successfully boot from it and log into my account but shortly after I log in, the hard drive shuts down and the computer is stuck.
Any ideas? Any help would be wonderful!

Answer 1

You are right. It is failing. I took my Mac into the Apple Store and talked with a genius. Although the hard drive would not do what it had at home (typical when you're trying to get something diagnosed) I shut it down so he could hear the noise I do.
Sure enough, he said the noise I heard was the drive read head hitting its start position. When a hard drive shuts down, the drive head moves out of the way since the "hard disk" is actually a thin floppy magnetic disc. The noise I kept hearing was indeed the drive trying to shut down.
Fortunately, I did make a clone of my internal drive to that external drive 6 months ago so I was (eventually) able to copy over all the important files, update the external clone and boot off of it.
Sure enough, tonight, I opened Disk Utility and it said in plain red letters that the drive had reported a hardware failure and should be replaced.
Since my iMac is Summer 2001, the Mac Genius said they no longer carry parts for it so he gave me the name of a local place that would be glad to fix it up. I called them and luck would have it that they were completely out of the internal drives used by my model iMac. So I have to check next week to see if they have received more in yet.
The good news is I can get a slightly larger interal hard drive since I was down to 10GB of a 60GB factory drive. So far, I hear I can go as high as 160GB but the RPM must be lower since my iMac has no fans.
Thanks for your help! As much as I didn't want to believe it, you hit the problem right on.