I've been using Microsoft's free antivirus and antispyware for several months and i've come to the conclusion that it simply sucks. I've recently been noticing some odd behaviors in my computer and with a free online scanner from Eset, realized that i have several trojans on my computer. Needless to say, i was extremely disappointed in the performance of Microsoft's free antivirus, because free doesn't mean it has to suck. I've used Avast's free antivirus for years and have had great luck with it. If anyone just needs the bare minimum of protection, i guess Microsoft's product will do.