I believe the OS is corrupted and I want to reinstall it. What is the procedure?
You would need to request the installer from tech support, wait for them to reply, and maybe give a proper reason for asking as I'm not sure they just go and give their that OS easily.
Try the reset 1st, if that fails then contact support.
You could try resetting it:
Note: This will, obviously, erase all of your settings and preferences.
bought used haven't set it up yet, can you just reinstall the OS?