Have you considered using a virtual PC system like VMWare or Virtual PC?
Of course, I am assuming that the reason you are installing this number of OS's on one system is because you want to test/learn each one. A virtual PC software is the best way to do this. I have Windows 3.11, Windows 95, Windows 98, Windows ME, Windows NT4, Windows 2000, Windows XP, Longhorn, RedHat 7.3, RedHat 8.0, Redhat 9, Redhat AS 2.1, Redhat AS 3, Mandrake 9.1, Mandrake 10 (installing now), Fedora Core 1, Slackware 9.1, and FreeDOS installed on VPC's. I can boot to each of them without having to reboot my host OS. I can play with them, break them, fix them, reinstall them, all without having to risk my host system.
As to configuring grub....
Most likely, grub was installed by the first linux distro you added to the system. The grub.conf or menu.lst file will usually be found in /etc on the RedHat/Fedora distros. If you installed grub manually then it's going to probably be in /boot/grub.
The best guide available as to what to put in the configuration file can be found at http://www.gnu.org/software/grub/manual/grub.html.