Finding you Steam ID:

Open L4D and start a game (multiplayer, singleplayer.. anything) then open the console (usually the top left key, ` on uk keyboards) and type "status" without the "quotes" and copy the full line where you see your name.

example...

# 1234 "Your Name" STEAM_A:B:CCCCCCCC 1:38:00 68 0 active

Note: The bit before the colons ( : ) (the A & B ) bits ARE required, not just the larger CCCC.. player number



thanks,

Monkey


Console problems:

If you can't bring up the console, make sure it is enabled
In game, go to options, Multiplayer options, Keyboard options and select enable on 'developer console'