Best antimalware: Spybot Free

Spybot is dedicated to seeking out and eradicating the little things your antivirus won't catch: tracking cookies, spyware, browser hijacks and the like. Unlike antivirus, it's not an app you absolutely need to leave running all the time – an occasional blast is all it takes to clean up the mess and potentially leave your PC running faster.
For deeper protection, Spybot can assist you with switching off startup items, and immunise your machine against known malware sites and malicious cookies.
Once upon a time we might have put Malwarebytes Antimalware in this spot, but it's now available only as a free trial – if you have a problem that Spybot can't seem to fix, it's one to consider, though.