All scans are coming back clean on SpyBot, McAfee and Shredder. I got rid of startpage dc I think by getting rid of system32.dll and I found a back way into removing internet explorer. However, my CPU is still running 100%. Now what?

I've downloaded the Windows critical updates. I haven't downloaded a firewall yet. Will that help any of this or is there something else I need to do to get the CPU back to normal.