Trojan powerlik

My laptop started running very slow recently. I'm getting a Norton Box telling me my system is infected with trojan.adclicker and trojan.powerlik.  I'm also getting a message that poweshell has stopped working. I've ran a full system scan(Norton) but no results.  I have not run any malware scans.  I also noticed the busy circle blinking next to the mouse pointer.  I've also received several performance alerts saying high cpu usage.  Any help would be greatly appreciated.

Dave