How to kill a process that keeps saying access is denied?

Ok so I had been lagging in many of my games I've been playing recently, so I opened task manager and found my CPU Usage was at100% constantly. I downloaded Process Explorer and found that "FahCore_a4.exe" was taking up 22% of my usage...and there are four of them running all taking up 22% or more of my CPU Usage, however, It wont let me kill any of them. Ive also tried psikill, it keeps telling me my access is denied. Any help would be appreciated, thanks.