So I was playing TF2 earlier when I noticed this: I can't move the camera as I'm walking,so I can only look straight ahead. And what I mean by that is that I can only see in 1 direction unless I'm standing still. This has never happened before,and I'm assuming this problem will be the same for Portal 2. I just want to play without having to be stuck looking one way as I walk around. Also I use a touchpad,not a real mouse and I have an Acer Aspire (specification help for better results!). I already tried all of the options in the Options Menu,but it doesn't help. I honestly don't know what to do.