Here is an interesting comparison of Cortana over the course of the 4 halo games:
PTesh adds his dulcet prepubescent tones over the top of one of the new trailers for weapons...
Try upgrading your browser to Google chrome (you wont regret it). There is probably an IE...
Proceed through the level as you would normally until you reach a dark tunnel where you need a flashlight. After that, hop in a warthog and continue through the level. As are about to enter the giant tunnel, turn around and go back to the spot right after the dark tunnel. If you are looking straight out from that tunnel, follow the path on your right (not down the road, but against the wall) until you reach a porch type area, there will be a warthog on it that is completely invincible like the ones in Halo CE.