Steps to removing Mac OS?
You cannot 'remove' the Mac OS. The computer will not function
without it. Macintosh computers need, and can only function with,
the Mac OS.
What you can do, possibly, is revert to an earlier version of
the OS, if you still the disks the computer came with, or you can
possibly upgrade to newer OS than the one you are currently
using.
If you want to revert, then insert the installation disk and set
it as the start-up disk and then follow the onscreen instructions.
This will delete the existing OS and install the desired one.
If you are upgrading, insert the installation disk and set it as
the start-up disk. Then follow the instructions. This will upgrade
the existing OS to the newer one.