Someone threatned to overheat my computer?

Ok I play this game called habbo which is for teenagers but some adults play it (don't ask me why) And they know how to hack accounts and overheat computers I know their not bull shitting because they did it to my friend because it overheated and broke. How can I protect my computer from this. I have avast (free version) So my anti virus isn't too good. All answers are appreciated. Thanks