How come my left 4 dead 2 game on steam always crashes after the beginning clip?

It says "Steam is not running. You must start Steam in order to play this game." But I do have Steam running and all my other games still play?! HELP!!! NEED MY L4D!!

: Left 4 Dead 2 CTD (crash to desktop) fix
Fix :
1)Navigate to your windows folder (usually c:/windows/)
2)Inside there, goto the CSC folder
3)Try to open the folder and it should fail (if it doesn’t, you have a different problem). It’ll come up with ‘You don’t currently have permission to access this folder’ at which time you keep pressing continue until it says you’ve been denied.
4)Right-click the folder, go to properties.
5)Go to the security tab at which point it’ll say ‘To continue, you must be an administrative user with permission to view this object’s security properties’ at which point you click continue.
6)Click on admin in the owner tab which will swap the owner to the administrator then click OK.
7)You then click on OK once again which will bring up the security tab.
8)Tick ‘full control’, press OK twice to get out of the properties tabs.
9)Run the game.

From http://www.gamingnewslink.com/2009/11/18/fixing-left-4-dead-2-crashes-freezes-and-steaminstall-errors/

Credit goes to them