from a live cd click to open a terminal (terminator, xterm, console, rxvt) and type the binairy-command grubinstall (grub-install, grubinstaller) or liloinstall. The syntax of the command might be slightly different at each distribution. -setup -config -conf -cfg might perhaps work also. Search for grub and lilo at the find GUI. Executable files have special icons.
Watch out for the filesystem support of grub. If you use a fs that is uncommon like freeBSD-ufs grub might not be able to read it.