why two hardisk on a ide line.one cannot work.

why two hardisk on a ide line.one cannot work.
speak in chinese.
one line :40g ide disk and a video driver. (master sisterm)
one line:120g ide and a 80g ide.
120g can not work.
and get down the 80g ,the 120g can work.if no ,can not show out on my pc.
what i can do in bios