Why is my new gaming PC running slower than usual all of a sudden?

hii,
I have this problem to and i don't have a clue how to solve it, if theres someone seing this post i would appreciate your response. i know its not the best pc, but i was running rust very high settings no problem 70 FPS, and now its just been cut in half? same with overwatch. i've scanned my computer for viruses and nothing has come up and im sure it's not overheating. Any advice?

Thanks!
I didn't find the right solution from the Internet.
References:http://www.tomshardware.com/answers/id-3...ual-sudden.html


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