The Emergency boot disk is created at the time of os3.9 installation. It is a bespoke disk designed to work with the ORIGINAL hardware profile. If the hardware profile has changed since it was created, then it wont work.
You can try to make it recognise your Arhcos by editing CD0: in DF0:Devs/dosdrivers to point at your CDROM device driver and unit number. You must also put your CDROM device driver into DF0:Devs
The disk will be nearly full, so you may have to delete the old CDROM device driver to free up space.
