I keep crashing and lagging. PLEASE HELP

So i've been struggling with this for months now. And now i'm absolutely sick of it. My league keeps crashing if i close it. Let's say that i'm in the middle of a league game and i wanna listen to youtube. I close my league and put on youtube. But then, when i click on the league button again, it crashed. And i have to restart my whole league of legends. Which is really anoying. And i also get a lot of lagg sometimes, while everything else on my pc works fine. I've been getting this problem since i downloaded plays.tv which has been a few months ago. I have the same problem with some of my other games. Please help me!
Report as:
Offensive Spam Harassment Incorrect Board