Use the first CD to boot, and type "linux rescue" at the boot prompt.
When you get to the command prompt, do the following
#chroot /mnt/sysimage
#lilo (if you use LILO, do "grub-install /dev/hd*" where * is your hard drive number, if you use GRUB)
CTRL+D
CTRL+D
The system should reboot and the boot loader should be restored.
This is assuming you have not made any changes to the partitions. If you made changes to the partitions, it will not work.