For the past couple weeks now, Portal 2 won't start for me. I launch it, then after a couple seconds it dings then says 'missing executable'. I haven't had any luck with it. I figured my best bet is to completely delete the game off my PC entirely then reinstall it, so I delete all the local content from my library and reinstall it, but it does a quick ~40 MB update and gives me the same problems. I could probably manually delete everything, but I want to see if there is a simpler solution first. Thanks.