OS 10.5 - Mac Pro freezes at Apple Logo and spinning gear screen

All of a sudden my Mac Pro stopped working properly. It started by freezing when my screen saver same on. Then it froze when I tried to launch iTunes. Now it freezes at the loading screen every single time. Foe the past 12 hours I have been reading troubleshooting tips online which include doing a hardware test (which showed no errors), starting in Safe Mode (which I am unable to do for whatever reason), using fsck (which I have done several times with no changed result), and trying to boot from the disc to use Disk Utility (which I am also unable to do).

Is anybody able to help me? I am really at a loss and I have extremely important files and programs I need to get a hold of...