Need help reinstalling X.Org 7.4

Can someone help me reinstall xserver 7.4? I had upgraded to a beta version of 8.10 and it messed up the xorg.conf because I have an ati video card. I had read that I needed to downgrade xserver at the time to one that was supported. I was able to remove xorg 7.4 but since can't access the internet from the root shell I don't know how to reinstall xorg from the live cd. I would greatly appreciate any help on this because I don't want to resort to a full reinstall of Ubuntu. Basically, I can only access the shell from the recovery mode. Thank you to anyone that attempts to help me.

You could try booting the live cd and using chroot to install xorg. This would require you having a working internet connection while using the live cd. Open a terminal (Applications>Accessories>Terminal)

sudo mount /dev/sda1 /mnt 

sudo fdisk -l

Then chroot

sudo chroot /mnt

sudo apt-get update

sudo apt-get install xorg

sudo umount /dev/sda?

Thank you for responding. I had found this solution on another thread right before you had replied and it worked. Thanks again for your help.