Just to make sure we are on the same page, this is my understanding of your current situation.
- You now have no /etc/X11/xorg.conf (good)
- When you boot the os it "locks" up and you then turn the machine off using the power button (bad)
Do you know what is causing the lock up? Is it X trying to start? If so, you can disable X from automatically starting at boot.
To do this boot up the machine using your live usb image, mount your hard drive and move the X startup script:
mv /etc/rc2.d/S01gdm /etc/rc2.d/K01gdm
The above assumes that mint has inherited the standard sysv style init that Debian uses. You will probably need to modify the above command slightly.
Anyway once you've done this you should be able to boot up your system as normal with the exception that X will not be started. Then you can have a poke around and try to understand the root of the problem is.