Invalid node structure/retrieving data

Hi there.

I have a SL iMac desktop about four years old that was working fine up until recently. My Mac mail started freezing up my computer forcing me to perform hard shut downs. A month of issues (I thought it was due to my HD getting too full) eventually led to my computer not being able to boot past the white logo loading screen followed by it switching itself off. Realising there was something bad going on (excellent guess wouldn't you say.) I started trouble shooting.

I can't boot in safemode at all - I'm not really sure if my computer is capable of it anyway though I think it is the right version.

Executing fsck lines brought to my attention the first 'Invalid node structure' error followed by the disk utility 'verify' option off the OSX disk with the same result.

My problem is just as my computer crashed I was about to buy a terabyte external hard drive because my old external simply was too small. Now I have half a computers worth of files stuck on a system that won't launch that's looking like I'm going to have to wipe and rebuild. I came across a help forum that told me to connect my computer with a MacBook via firewire which I have done but the problem is that my iMac isn't coming up on the laptop in any way shape or form so I can't pull any files off my damaged disk.

As a motion graphics student I have a whole art folder left on there I am desperate to retrieve. Is there anything that can be done? A manual way to locate the iMac?

Also if I run diskwarrior as everyone seems to recommend will it 100% wipe my files? If it will and I can't retrieve my data, should it come to biting the bullet will just wiping and reloading my OS on from scratch clean up this invalid node structure error?

As you can see I'd love some advice on this. Appreciate it heaps. Cheers guys!

I'd get the drive removed and replace it with a new one. Put the old one in a FireWire external enclosure then use Data Rescue to try and get your files back.

While formatting and re-paritioning a drive will mark the bad blocks once a drive begins to die I wouldn't trust it with real data.