Game startup

So I used to be able to play on my laptop just fine, but since one of the more recent updates it has stopped working completely. I open League, join a game, pick a champion, and everything loads fine! But once I enter the game, my whole computer freezes. I can't switch to my desktop, I can't open task manager, nothing. All I can do is manually turn off my computer and turn it back on. I've tried EVERYTHING they say to do to try and fix it, but nothing worked and now I don't know what else I can do.