In a sense, it's not an all-in-one solution like the others. True, it has anti-virus and anti-spyware but where it differs is that it's not trying to shovel in all sorts of other features that a) you don't need and b) often only serve to destabilize your computer. Microsoft Security Essentials isn't trying to compete against other products long feature list - and as a result it wins.
It is the world 2nd popular antivirus program and its free.we don't even need the update it, it updates when windows update so turn on Windows Automatic Update and turn on the Windows Firewall when you travel.I have been using it and it hasn't caused any problem in my computer like other antivirus program has done.I have 512 MB ram it hasn't cause any problem in my system and i don't think it slows down computer It haven't slowed down mine.I have used many other antivirus programs like Avira ,AVG ,Kaspersky etc. Microsoft security essential is best for my system. I recommended it to you you should try it. Besides Microsoft Security Essentials might not be the right solution for everyone.No single product is. Hope this helps