Trying to wipe a corrupt 2006 iMac w/o success

My 2006 iMac is showing signs of hard drive corruption — it freezes without warning and nothing short of a hard reset will get it moving again, so I decided to erase & replace. However, in Disk Utilities, the Erase and Repair Disk options are unavailable. I did manage to run Verify and it said the disk was corrupt. It refuses to open in Recovery Mode and I could not partition the drive to erase even a portion of it. I tried Single User Mode fsck -fy, which ran and said that the disk was OK, but after I rebooted, I was still unable to use the Erase function. I do not want to send this machine off to the recycler with sensitive info on its hard drive, but it's looking more and more like I may need a sledgehammer.

Was looking for a way to connect it to my newer iMac via the network and try to repair it as a target disk but could not find any way to do that without a firewire cable, which I don't happen to have. So what's the verdict: Do I order a firewire cable and attempt to repair this disk just so I can erase it, or is it easier to just use the Hulk Smash modification method? All important files have been copied to a flash drive so there's nothing on this that I need to recover, I just don't want anything that's on it to be recovered by anyone else.