If you followed the dual boot video on the wiki that means you created a /boot partition so your problem is /boot is not mounted when you run the lilo -v command. You have a few options...
1) edit /etc/fstab to allow /boot to be mount automatically at boot time. (This is generally frowned on a defeats the purpose of a /boot partition.)
2) Mount boot by command line whenever needed. For example if /boot is at sda2 like in the video one would do this..
purehate@pwnsauce ~ $ mount /dev/sda2 /boot
Then just make sure your kernel is in the boot directory...
purehate@pwnsauce ~ $ cd /boot
purehate@pwnsauce /boot $ ls
boot config.bak grub kernel-2.6.25-gentoo-r6 lost+found memtest86
purehate@pwnsauce /boot $
Your looking for vmlinuz which is the name of the backtrack kernel by default.
*note Obviously I'm using another OS but the commands are the same.