On Cent OS 4 the very last screen says REBOOT. Before
click that do CTRL-ALT_F2 and get a prompt.
then enter the following commands.

This will allow the software raid arrays to boot.

grub
find /boot/grub/stage1
device (hd0) /dev/hda
root (hd0,0)
setup (hd0)

This is easier the setting up mdXXX commands after boot.

Jerry