[Wolferion]

1) Download original Steam : http://cdn.steampowered.com/download/SteamInstall.msi
2) Download this engine : http://rapidshare.com/files/174925285/engine.dll.html
3) Replace the one in your Left 4 Dead/bin folder.
4) In team press add non-steam game and add the Run_L4D.exe or whatsoever you have to start directly L4D.
5) In Steam, go to Community and join a group. I am in L4D Server's  group ( 5,723 Members  , dozens of servers )
6) Run L4D through Steam, enjoy