Ok, first thing to do is go into the bios and make sure that the bios can actually "See" this drive.
Let us know if it can or can't.

both hard drives show up in the bios

Ok take the back off the case and make sure the IDE ribbons are secure to both the drives and the motherboard.
If they are and you still get that message then the drive could be toast.

i checked the ribbons, they are def in ok.

My final resort would be to slave it in another pc and run a chkdsk on it from there. If it either doesn't find it or comes back with errors then bin it mate.

both hard drives show in the bios ok, but not on 'my computer'

Shut down and disconnect the hdd's and reboot.
Shut down again re-connect the hdd's and reboot and see what that brings up.