hey ven,an antivirus is a must,no matter what anyone says.avast is good and unless your running a pentium d,will not slow a thing down.there is an order when you have a slowdown that you think might be malware.first run adwcleaner and remove whatever it comes up with.next run junkware removal tool.it will remove anything it comes up with.finally do a scan with malwarebytes and do the same.me,i run avast,malwarebytes premium (paid version) and malwarebytes anti exploit free version.im running all this on an old phenom triple core with 4gb of ddr2 ram.if it aint slowin me down it sure wont slow you down.lol