Episode 2 not letting me change controls, audio settings

[StonedMagician]

I am currently playing through the HL series, and found that Episode 2 has controls that differ from HL2 and Episode 1. However, when I change them, quit, and play again later, the controls and audio settings have reset themselves. The upshot of all this is that I have to readjust the controls and audio settins every time I start the game. How can I fix this issue?