OK I have used 4 ratings to determine the best AntiVirus out on the market. Fourth place is Microsoft Security Essentials. Tests VB100: Passed VB100 RAP: Failed (score 90 or more to pass) AV-Test: Passed (score 8/12 or higher in combined protection/repair) AV-Comparitives: Failed (Score 15 or more combined in the tests) Grade:2/4 100% Summary: Microsoft Security Essentials failed 2 tests of the four. It failed the RAP test in which it scored less than 90% and rated only standard by AV-Comparitives. It also had a very low protection rate by AV-Test.org but made up for it by scoring high in repair rate. It's user interface was third best behind Panda Cloud and avast! so anyone can use it. That said with it failing 2 of the 4 tests I would recommend AntiVir or if you want simplicity to go with either AVG or avast until Microsoft can increase it's protection rate and rate higher on the RAP test.