Dead drive? Can't erase

My iMac is 2008. Dug it out to see if I could get it going. It won't boot normally so I'm boring up using external thumb drive with OS X.

I got on disk utility and it sees my internal drive. I try to erase but get this message:

Erasing Macintosh HD and creating Macintosh HD.
Erase process has failed.

Unmounting disk, couldn't unmount disk. Operation failed.

Any other way to erase? Or is the drive dead?

Thanks

via ehMac.ca http://ift.tt/1Kn2TOL