Why is my computer slower than normal?

I've been able to play League of Legends when my computer (fujitsu lifebook ah530) was new on decent graphics no problem. Now, it seems like it just refuses to run like before with a frame rate of 2 fps at lowest setting. This computer should easily run this game. I have resorted to even system restoring it and it still runs slow. I dont know if my processor slowed down or if my graphics card isnt working as well, or even if I have some kind of hidden spyware or virus I dont know about. I would really appreciate the help, thank you.