Well, for an example, check your /etc/lilo.conf (cat /etc/lilo.conf)
Mine goes like this:
# End Slackware
image: Most distros will use /boot/vmlinuz as startup kernel (FIXME) but to check anyways, say ls /boot
to see what's hangin' out there.
root: Of course, you need to know on what partition your second Linux distro is. To see, say fdisk -l
label: Anything of your choice.
read-only: My lilo.conf said 'any non-UMSDOS partitions should be mounted readonly. I think this is corrent, since fsck might want to sweep around for bad blocks and stuff, and then you really want your partition mounted readonly.