Malware has taken over computer

I have a program scanning my computer stating it is MS anti-spyware program. The program has changed my desktop picture, will not allow me to run malwarebytes, Avira, Hijac or any other program. When I log onto the internet it immediately freezes the screen. I am unable to navigate with the mouse or the keyboard. I was able to run malwarebytes and Avira in safemode. Both programs stated all trojans and so forth had been removed. However when I rebooted the computer the program was yet there. Please help.