Did this kernel panic show up at reboot right after having re-attached the unplugged devices?
In this case it could be related to different device names get assigned at your hard drives: if with your extra devices unplugged, the Slackware root partition was found let's say under /dev/sda1, with the extra device attached at reboot it may be that the Slackware root partition is actually found under /dev/sdb1 or /dev/sdc1 (if one of your new device get assigned the name /dev/sda first).
I suggest to try to boot the system with the Slackware installation dvd. At prompt just try to figure out under which device the Slackware root partition is located (fdisk or similar can help you in doing that). Once you got this information reboot again your system (without removing the Slackware installation dvd) and at Slackware installation boot try something like that:
Code:
boot: huge.s root=/dev/sdXN rdinit= ro
where /dev/sdXN is the partition containing the Slackware root partition.
Finally if you are able to boot the system in that way modify your /etc/lilo.conf and /etc/fstab accordingly (providing also there the right root partition and boot device). Run lilo again, remove the installation Slackware dvd and reboot your system to check if now the problem is fixed...
Good luck!