My TF2 is so bad

Hey,

if anyone can help out with my problem, feel free to post,
iv just brought the orange box for pc and installed it, all the games are added to my steam accout, but when i select TF2 it loads, but then i select any menu item and the music freezes for a sec, but then stops.
then i go to selct a server to play on as anyone would do, i find a server and join it but when it tells my im on my way to it, the loading bar in the bottom right stops loading and my TF2 crashes resulting in my computer restarting or the screen to go blank! >
if anyone can help, please do!