Help! computer will not stop freezing?

Okay, so i've tried asking this question several times before, but some still aren't grasping that I CAN'T get onto my desktop. I am STUCK at the login screen. Mouse wont move, keypad wont type. It was working fine two days ago, but when I started up my computer i was unable to log on. I've tried restarting it in all the different types of safe modes as well. Please help!! Thanks :)