10-04-2012, 11:38 PM
In order to do any kind of basic trouble shooting whether it be to verify the hard disk or run the Apple Hardware Test, you need your install disk. You say the computer is a 2007 iMac so it probably came preinstalled with Tiger or maybe with Leopard. Both of those original disks are hard to find and can be expensive to replace. And any kind of professional repair by Apple or an authorized Apple dealer is going to cost $$.
Why don't we try this.... do you know how to boot your iMac to single user mode? No? Here's how: Reboot your iMac and hold down the command + s keys as soon as you hear the Bong! sound.
Follow these instructions:
At the command-line prompt type:
Press Return. fsck will go through five "phases" and then return information about your disk's use and fragmentation. Once it finishes, it'll display this message if no issue is found:
** The volume (name_of_volume) appears to be OK
If fsck found issues and has altered, repaired, or fixed anything, it will display this message:
***** FILE SYSTEM WAS MODIFIED *****
Important: If this message appears, repeat the fsck command you typed in step 2 until fsck tells you that your volume appears to be OK (first-pass repairs may uncover additional issues, so this is a normal thing to do).
When fsck reports that your volume is OK, type
reboot at the prompt and then press Return.
Your computer should start up normally and allow you to log in.
Let us know how it went.