You can create the mtab entries with a shell via ethernet.

rw
mount -o remount /dev/hda5 /
mount -o remount,ro /dev/hda4 /drive0
ro

cat /etc/mtab and see if it's reasonable. it should be something like:
/dev/hda5 / ext2 ro 0 0
/dev/hda4 /drive0 ext2 rw 0 0