I didn't really understand your problem, but this info may help you:
lilo is a bootloader that loads linux and also gives you the option to load other operating systems that you may have installed on your disk (such as Windows, or even another linux).
A bootloader can be installed in many locations, such as a floppy, a CDROM etc. But most people install it in the Master Boot Record (MBR). This is a special location in the hard-disk that contains information about booting operating systems. (keeping it very simple)
The /etc/lilo.conf is a configuration file that contains information about the operating systems and which partitions they are installed in. A typical lilo.conf looks like this:
# LILO configuration file
# Start LILO global section
boot = /dev/hda
timeout = 50
# VESA framebuffer console @ 800x600x64k
# End LILO global section
# DOS bootable partition config begins
other = /dev/hda1
label = windows
table = /dev/hda
# DOS bootable partition config ends
# Linux bootable partition config begins
image = /boot/vmlinuz-ide-2.4.26
root = /dev/hda9
label = Linux
read-only # Non-UMSDOS filesystems should be mounted read-only for checking
# Linux bootable partition config ends
Keep in mind that this lilo.conf file will not work unless it is intalled in a rescue disk, or in the MBR.
So, to load lilo into the MBR, you need to run /sbin/lilo
It is always a good idea to keep a rescue disk handy, as the MBR can be easily over-written by a virus, or during installation of another operating system such as windows.
Now, I have never used mandrake, so I dont know what rescue disk you were mentioning.
However you must keep in mind the following things:
1) You need to somehow load lilo into the MBR.
2) The lilo.conf file that you load should be checked that it contains proper information about all the operating systems on your disk.
3) If your lilo.conf file is improper then you won't be able to load the operating system (which apparently is happening now)
And finally, if you cant figure out what the HELL I'm talking about and you dont have any important data on the hard-disk, just format and reinstall everything