LOL freezes computer?

Hi, for 3 weeks now i amencountering a huge problem. in the first week the voice was bugging with a weird sound and fps drped from 180-220 to 25-60 2nd week lol started lagging even more and the voice was even more annoying 3rd week lol started freezing entirely i cannot press neither esc nor ctrl+alt+del i just have to restart the computer entirely. this happens while i am playing usually around levels 3-12 every time. i tried re-install and repair nothing happened.pls guys i am helpless