Do you have another computer that you could swap out the HD into.
I have heard it is possible to install on a different computer, then put it into the older computer before the first boot. That should configure xorg properly. If not, the following will do it:
PS: If you can't boot from a CD, I would consider setting a separate partition to store future updated ISOs when Intrepid is no longer supported. In fact, consider using Hardy for the extra year of support.
sudo dpkg-reconfigure -phigh xserver-xorg