I have L4D running in almost in gold in an xp bottle. It runs best when it is installed ALONE IN ITS BOTTLE. installing ANYTHING else broke L4D to where it dosent work at the menus. The only thing that is stoping me from rating this app as gold it frame rates at 15 when on xp (same hardware) i can get 50. However this might also be realted to nvidia's linux drivers.
BTW this is an unedited bottle, i havent messed with regedit and GLSL thing (what is this) or the fbo.