Adware.Win32.Mnless.cg病毒怎么杀??????????

瑞星提示c:\Documents and Settings\All Users.WINDOWS\Application Data\Microsoft\PCTools\染毒
    病毒名:Adware.Win32.Mnless.cg
因pctools.dll是只读系统文件无法删除,这该咋办,请高手指教!!!!!!!!!!

用户系统信息:Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.8.1.14) Gecko/20080404 Firefox/2.0.0.14