Where can I find Left 4 Dead and Left 4 Dead 2 soundtracks?
Do they officially exist?
There is no official soundtrack, as far as I know, but you could try the Left 4 Dead wikia Soundtrack page, which has all the different songs from both games arranged in nifty little youtube clips.
For posterity (and those without good net);
You can find them in your game directory, most of the actual music (you can find all the other scores and sound bytes in these folders) resides in;
These are subdirectories of your game directory which would normally be located at;
(the duplication of the