Just bought the game HELP!!!

[Gaydolf Titler]

I have just bought left 4 dead 2 earlier and downloaded and every time I play the game it shows the video and then goes to a loading screen. While its at the loading screen a pop up from outside the game asks me to download steam add on installer. But the game crashes and I can click anything. What im asking is if there is a way to download the steam addon installer without starting the game. PLEASE HELP !!!!!!!!! Thank you :D

[Bäd Apple]

Go to C:\Program Files (x86)\Steam\SteamApps\common\Left 4 Dead 2\bin and open the addoninstaller.exe