I'm sure I explained this
somewhere else...perhaps a little searching?
Cut a long story short:
Install one distro (let's say, Mandy).
Install the boot-loader (Lilo).
Install RH.
Do not install RH's boot loader.
Boot to Mandy.
Mount RH root (
/) partition.
Copy RH kernel image (from
/mnt/RH/vmlinuz) to Mandy's [/i]/boot[/i] directory.
Edit
/etc/lilo.conf.
Give extra option to boot from RH kernel.
Run
/sbin/lilo.
Reboot.