Laptop as monitor

Hello,

im just wondering can you use a laptop as a pc monitor,
Reason being as have a pc that is hd only because thats how ive set it up
and I dont have a vga to hd, etc

and I need to go to my parents to use there internet but the only have a box tv not hd
but they have a laptop with a hd port on the side, its a hp but dont know what though

will I be able to connect my pc to there laptop through a hd lead?
Im only need to know as it need update for windows, drivers and virus definitions on norton 360

thanks alot