Cannot Load to Linux OS When Change Motherboard

You probably need to make new initrd (kernel)

1) Boot with Linux rescue CD and let it search Linux installation

2) At rescue console,
    # chroot /mnt/sysimage
    # cd /boot ..where initrd located
    # mv /boot/initrd-2.4.21-32.EL.img /boot/initrd-2.4.21-32.EL.img.old ..rename old kernel image

3) Check /etc/modprobe.conf and make sure all drivers specified are accurate with new motherboard.

4) Rebuild existing initrd image:
    # /sbin/mkinitrd -v -f /boot/initrd-2.4.21-32.EL.img 2.4.21-32.EL

5) Reboot

Note: 2.4.21-32.EL is kernel version number

This is a guide only. I am also at beginner stage. Correct me if I'm wrong.