Ok, first, you need to get your Slackware root partition mounted, so create a mount point:
# mkdir /mnt/slackware
Then mount Slackware's root partition:
# mount -t ext3 -o rw /dev/path to physical slackware root partition/mnt/slackware
This is assuming your Slackware partitions are ext3 - substitue the correct file system as appropriate.
Ok, now Slackware's root partition is mounted, you need to check the PATH to the kernel and initrd file. It'll probably be in the /mnt/slackware/boot directory.
Then you need to edit your lilo configuration file: etc/lilo.conf.
As root, add the entry for Slackware, making sure you've checked the PATH's and the correct physical address of the root partition on your drive(s). It'll look something like this:
Code:
image=/mnt/slackware/boot/vmlinuz-xx.xx.xx
label="Slackware"
root=/dev/path to physical root partition
initrd=/mnt/slackware/boot/grub/initrd.slack
read-only
Where vmlinuz-xx.xx.xx represents the version number specific to your slackware image file.
Save lilo.conf, then in your console as root run lilo:
# /sbin/lilo (or it might accept just lilo)
Reboot.
Job done.
If you get any errors, (kernel panic - no initrd found) is the most common)) then you have the PATH to the initrd file incorrect.
This method works for nearly all other Linux distro's... Multiboot away!!