Half life 2 won't start

[macca400]

Hi
today i installed Half life 2 on to my new pc (its the version that comes with counter strike aswell) but when i launch half life the screen goes blank and the load cicle come up but it doesn't turn and when i go to task manager it comes up saying that hl2 is not responding. the updates have been downloaded from steam so i cant see what the problem shoud be,there are no error messages, also death match works perfect (hl2 multiplayer game) and so does counter strike

im using vista 64

thanks stu