Try
Ontrack's diagnostics to see if the file system and physical drive is intact. If it is, it will tell you. If not, it should give you clues as to what the problem is.
Another option would be a low level format through the BIOS, if your mobo BIOS supports that feature. Takes a while, but basically renders the drive back to new specs as far as the platters are concerened.
Seagate use a proprietary ontrack proggie to do this as well. Have you tried seagates' software??
Also, dunno if most of seagate's drives are firmware upgradeable.
And just a question: you didn't have a DDO loaded, did you? That would cause some of those problems. Is it an old system??
G'luck.
Cheers
Mick