"LILO" (LInux LOader) is a small program which installs itself in the very first sectors of your hard disk and allows you to launch Linux from the partition in which it is installed. But LILO is equally sufficiently sophisticated to handle several operating systems. Thus, you can choose which system to start under by typing "linux" or "dos" when restarting your machine.
Install LILO in the MBR (Master Boot Record) of you disk if there is not already another "multiboot" installed there (otherwise the other one will simply be overwritten).
You absolutely must install LILO otherwise your Linux system will not restart (except with the LILO disk of the previous section). If another operating system is already installed, be just as careful to make sure that LILO takes it into account otherwise the other operating system won't work either.
You can modify the parameters of LILO once your Linux system has been rebooted, by editing the file /etc/lilo.conf, then rerunning LILO by typing "lilo".