What is wrong with my computer?

it obviously has some ind of virus but ts weird. it hasnt slowe dmy computer down at all. in fact...its been alot faster than usual. but on the contrary, if i search something on google, i will click on a link and it will redirect me to a random website. then theres this random box that shows up that looks legit and it says windows XP on it and it has me type some stuff in so the computer wont shut down. and im getting alot of popups. i tried downloadng AVG and avast but they wont download. its crazy. what should i do