safe boot mode and sound issues

Hello.....I have an older version imac intel core duo2.16 ghz 2 gb mem.......This is my problem. I ve had this computer for awhile now, so I was kinda expecting something to go bad on it, from all the years. anyhow, was on the internet and screen froze up with green wavey lines on it. so i rebooted and it now it never gets to the log in screen, just has arrow cursor left hand corner, which i can move, but a still picture of the arrow stays in the corner lefthandside. Ive looked at a few forums, tried a few things, but nothing. however i can boot in safe mode and the computer runs but picture has green lines everywhere. The green lines arent a problem, I could probably deal with the safe boot, if there was someway i could get my sound to work. Im an artist, musician, and use logic 9, and an m audio interface to record music everyday of my life. Now I am aware that some things do not work in safemode but is there any way around this. Ive heard of extensions being added to run wireless in safe boot. Can i get my audio recording going in safe boot by doing this? if so, how? what extensions? what steps? I am willing to try anything due to the fact that my computer is no good to me if there is no sound coming from my interface. please help me, and if i can get some clarification on what is wrong with my computer in the first place, that would of course be helpful also. thank you so much. please forgive my writing skills. i have very little education. i appreciate you taking the time

Safe Boot is a special startup with partial system activation. Some part (associated with audio) of your computer isn't working.
Have you tried repairing the hard drive after starting up from the original install DVD?

I think your motherboard is what has failed. Try Apple Hardware Test:
Intel-based Macs: Using Apple Hardware Test

I understand that my Imac somewhere is failing and is probably un fixable. But my question lies more in how do i get my audio interface and my sound to work in safe mode. what extentions can i add to make it run in safe boot and the ability to record and hear sound. is there any way?