I bay a laptop and installed bf3 and it work wery good . then I deleted it because my hard disck was full . After 1 year I installed it again and worked a lot worse. but I do not know why.
You have loaded your laptop with lot of garbage, that why it started working slow. it might got a virus as well.
Re-install Windows (if that's what you are using), and don't install every piece of BS you find online.