You do not need the CD.
First - on the GRUB prompt, touch anything and you will enter an interactive mode. Go to the upper option (usually your default) and press on 'e'.
Go down one line (to the longest one) using the arrow key, and press on 'e' again. Go to the end of the line using the arrow key, and add the number '3' at the end of the line, separated from the text preceding it.
Press on 'Enter' and then on 'b' to boot the system.
You will load the system in a text-only mode.
Login as root.
cd to /etc/X11
mv xorg.conf xorg.conf.date
(replace date with the current numerical date)
system-config-display (that should be the name, as far as I recall)
Follow the instructions, and you should be able to recover your out-of-the-box screen settings, as before.