Microsoft Security Essentials is Microsoft's own foray into the world of virus protection.
Ranked in these QuestionsQuestion Ranking
MSE doesn't seem too resource intensive
Pro Simple and Silent
Does the job without distracting you.
Pro Ease of Use
Pro Less prone to false positives compared to other solutions
Frequent false positives in themselves can reduce security
Con Used as non-competitive baseline since 2013
All except one tested antivirus scores above Security Essentials.