How can Red Hat Enterprise Linux system be accessed when booting into rescue mode or runlevel 1 is not possible?

If booting into runlevel 1 or into the rescue environment using the installation CD is not possible, there is still hope in fixing the operating system. The system might still be able to boot into "emergency" mode. This "runlevel" is even more basic than runlevel 1. It does not execute the /etc/rc.d/rc.sysinit script and it mounts the root filesystem in r...