skeez,
This is one of the most asked questions in all of forumdom, and you certainly should have just googled this. (that's why no one has replied) I will because I ran across some new information about Microsoft Security Essentials, that says that this free AV from Microsoft has many new features that make it a very attractive offering. In my estimation - I run a small tech service - most consumers choose AVG Anti-Virus, most techs choose Avira AntiVir Personal. Here's a paragraph from my latest tech newsletter:
Free Antivirus -- I know there are several out there – but I’ve said for years that a Free antivirus will never perform as well as a Paid antivirus. I am aware that Comcast and other internet services actually offer a free antivirus subscription with their service that most people never use or even know about. (You can log into your Comcast account, and download it for free under the Security area – It’s Norton Security Suite) But Microsoft launched their free antivirus product over a year ago called Microsoft Security Essentials, which was a very good product – and it didn’t take over your computer. Norton as well as many other big names have been known to severely degrade computer performance because their product seems to invade your entire machine. The newest version of Microsoft’s product inspects network traffic, checks Internet Explorer’s website for malicious scripts, and is a great malware scanner – and it’s free!