hdd with errors

ontrack diskmanager showed an unrepairable error at sector x. i have seen a resize-option and relation between sectors and kb/MB. if the error is at the end of first 1/3 i will loose at least 2/3. chas told me i could mark the bad clusters/sectors. how do i do this. my “tool” was making a special partition containing the bad sector- the only problem was make scandisk not to scan.otherwise system would halt.