Nope, not what I meant! The article at
http://www.answers.com/topic/head-up-display explains it pretty well. My father-in-law has the head's up display on his '03 'vette and I believe it was originally supposed to be on the '90 but GM had problems getting it up and running.
Unfortunately, there is a star crack on the windshield (that has been drilled/filled) but eventually we will need to replace the windshield. *sigh*