Fooling around in the System folder with invisible files showing !!
Gotta be careful in there - heh, but you know that now, I guess.
Try zapping the pram - hold Command, option, P +R keys at boot. Hold them down til you hear three bongs/chimes.
Try resetting the SMC - go here to find out the correct way for your machine http://support.apple.com/kb/ht3964
I'd grab a copy of disk warrior http://www.alsoft.com/diskwarrior/index.html
and try and boot from that - It should boot from the SL cd tho'.
The other thing I'd try is to boot from a firewire external OS backup if you've got one (or borrow one).
Another thing to try is to use an older Leopard install dvd and try to boot.
If trying to boot from cd/dvd hold the "c" key down before the bong if you've got a fw external OS then hold the option key and select the disc
If you do get an OS running then launch Disc Utility.
Select your HDD (manufacturer ID) in the left panel.
Select First Aid in the Main panel.
(Check S.M.A.R.T Status of HDD at the bottom of right panel. It should say: Verified)
Click Repair Disk on the bottom right.
If DU reports disk does not need repairs quit DU and restart.
If DU reports errors Repair again and again until DU reports disk is repaired.
When you are finished with DU, from the Menu Bar, select Utilities/Startup Manager.
Select your start up disk and click Restart
Try those methods first if they fail try booting in safe mode http://support.apple.com/kb/HT1455
- oh I see you've been trying to do that
If nothing works then post back - you may need further assistance.
edit: ohh just remembered this one from old OS X days. fsck - which stands for file system check
Boot Into Single User Mode
Start up your Mac and immediately hold down the command key plus the letter ‘s’ key (command + s). Your Mac will start up in a special environment that looks like an old-fashioned command line interface (because that’s exactly what it is).
At the command line prompt, type the following:
Press return or enter after you type the above line. Fsck will start and display status messages about your startup disk. When it finally finishes (this can take a while), you will see one of two messages. The first indicates that no problems were found.
** The volume xxxx appears to be OK.
The second message indicates that problems were encountered and fsck attempted to correct the errors on your hard drive.
***** FILE SYSTEM WAS MODIFIED *****
If you see the second message, you should repeat the fsck command again. Continue to repeat the command until you see the “volume xxx appears to be OK” message.
If you don’t see the volume OK message after five or more attempts, your hard drive has serious problems that it may not be able to recover from.