Your drive has apparently crashed badly. When you open DU do you see anything listed in the sidebar? Most likely you will have to try reformatting the drive before you will know if the drive has failed completely.
1. Boot from your Snow Leopard Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu.
2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.
3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed.
4. Select the volume you just created (this is the sub-entry under the drive entry) from the left side list. Click on the Erase tab in the DU main window.
5. Set the format type to Mac OS Extended (Journaled.) Click on the Security button, check the button for Zero Data and click on OK to return to the Erase window.
6. Click on the Erase button. The format process can take up to several hours depending upon the drive size.
After formatting has completed quit DU. Complete the installation of Snow Leopard.
I'm new to this forum and don't quite know how it works, but I didn't mean to say that my own response solved my own problem. I'd still like to hear thoughts or advice. My related question is whether it's worth driving 45 minutes to the Apple Geniuses or is it safe to go to a local store with a good reputation?
My computer booted just fine this morning! I'm happy but have no idea what went right. Here are the facts in case somebody can make sense of them or if they can help somebody else.
- Yesterday my iMac wouldn't boot and there was a flashing question mark.
- I tried a few things: disconnecting cables, doing a safe boot, etc.
- I finally tried to boot from the install disk holding down the "c" key per these instructions:
- Disk Utiities didn't show the hard drive in the left side list.
- I also tried to reinstall the operating system, but the hard drive wasn't visible in the left column.
- I shut down overnight.
- This morning I turned on the computer, forgetting that the installation disk was still in the drive.
- It booted! It showed the start window of the installation disk, but the window was different than the one I got with the "c" key.
- Behind the start window was the screen with my finder and everything else.
- I took out the installation disk, did a shutdown/restart and it was fine.
- I ran "first aid" from my hard drive disk utility, and it says the disk is fine.
That's all I know. It's very strange. Maybe the "c" key was the wrong thing to do, I might have misread the instructions, but the drive was completely inaccessible before and after trying the "c" boot.
I'm curious about what happened and if there's something I missed that might be helpful in the future. But thanks for the help!
I am still thinking your disk may be dying slowly. Make sure that you make backups even more regularly.
When the disk is going down the next time, do not bother too much about trying to revive it: harddisks are very cheap, you just buy the right size and replace the old one. An old revived disk will sonn die again.