Well, there are laws in some areas against having any video screen that can be seen by the driver. usually if the screen is for gps, or just display of music information (eg a regular headunit display) then its alright.
so no, theres no law against a huge screen, but its covered by the same laws that cover all the screens people here use.
Project AutoBoxen: Coming along, almost ready to hook up in the car.
Celeron 500, 192mb ram, 8gb hdd, other stuff.
'91 Mazda 626: Its free, so ill use it.