don't use a laptop, they break and get stolen easily.
what you want is a hidden carputer
use the screens as computer monitors(using vga, dvi or hdmi cables) and have an input from the head unit to the linein in the carputer.
install windows and winamp on the carputer and make winamp start at boot. with a playlist that uses the linein input.(ctrl+l---> then type in "linein://")
that way when you start the car its ready to go all the time, and nobody will know its there. when you want to watch the vis, you change the input on the monitors to the VGA or dvi(or whatever you used) input.
more info about carputers can be found at http://www.mp3car.com