You can do that if you comment out the initrd line in your /boot/grub/grub.conf or /boot grub/menu.lst file. Jut put a hash "#" in front of the line. If you can't get anywhere once booted up, you can edit it as you boot up. See the GRUB MANUAL
for more detail.
If you use LILO, do the same thing in the /etc/lilo.conf file.