Malicious software and viruses run in PC background and they start their own processes which are hard to detect by average PC user. A running program that has active process often can not be removed unless there is a way to kill its process running in system background. These malicious programs also make changes in registry and associate themselves with certain executable files. If you want to remove those viruses, you need a mechanism that stops their background running processes and fix registry. RKill is an antivirus tool that terminates known malware (running) processes so that you can clean PC from infections without interruption. RKill kills malware processes that are running, removes incorrect executable associations and fixes registry policies to make security tools run again which sometimes stop running in case of PC infections.