Assuming the 160GB is connected to an port on the motherboard and there is nothing unusual done with the Master/Slave jumpers:

The installer and "format" only list partitions that they could actually handle.

Depending on the actual filesystems used for OSX and MacOS9 this might not be the case.


Go to "Tools" and start "HDConfig", your drive should show up here.
How to continue from here depends on wether their is free space on your HD and wether you want to keep OSX/9.

There have also have been cases where drives don't show up, often shortly before those drives failed (160GB means >10 years....).