sounds like it is
Is everything still connected right.
Disconnect it and try it again or in another computer, if you do get it running copy the drive ASAP, also is S.M.A.R.T. turned on in your bios, it saved my uncle once
Correct me if I'm wrong, SMART watching the HD and alerts you if it thinks there is a problem.
Two years ago my uncle's computer started to give him a msg when he started up that the hard drive might fail and to copy his data. I looked at the computer and 5% of the Hard Drive was fucked up. I got all his information off and when I was done I checked again and it was up to 8%