Some files can be retrieved, yes. But only some will work, and most of them will have the model, but.no texture (weird purple and pink squares). Other than the way the other answerer mentioned, there really is no way. Just buy the games, theyre not expensive at all! Css is what, 20? Tf2 is free now, half life series is, well WAS, really cheap. Just wait for one of those to go on sale again, like for christmas on steam.
