Updated League on 9/4/2015 Totally slowed my pc and League was Glitchy

Im running windows 10. Leagues installed on a ssd drive. Gpu gtx 970 and running 16 gbs of ram. Now when i updated my league lastnight the first game was fine notice some lag, when i went to look around the map on summoners rift, but second and third game were unbearable. I had monitored my ping the connection was fine it seemed to be more the game itself. My pc at this point began to run so slow i couldnt even swap from league back to google chrome.

I uninstalled the game and my pc returned to normal. i later installed the game overnight and when i woke up today. The patch failed at 99% and i couldnt close league. My pc was running slow again.

Im just not understanding the issue everything was normal till this second update for patch 5.17.