If your thinking of changing your Anti-Virus software this might be the time. If your using a payed version, you might want to safe yourself some money and switch. Before last year I was using AVG FREE service, but each time it updated and did a SCAN I would see a noticable difference in my computer performance during that time. When I switched to MSE – I have no idea when the scan or update is happening.
This is a very light, easy to install and use Anti-Virus software, one that Microsoft puts out and just by the history of this product are working in keeping this product fresh and new.
Windows Firewall integration. MSE 2 integrates with the built-in Windows Firewall and will prompt you to enable this integration during Setup. This way, MSE can include firewall monitoring as part of its overall PC health monitoring.
New protection engine. The MSE antimalware engine has been updated to offer enhanced detection and cleanup capabilities with better performance.
Network inspection system. MSE 2 now helps protect against network-based exploits.
Other improvements. MSE 2 includes other important, if hard-to-find, changes. You can specify that CPU usage not exceed a certain limit (the default is 50 percent) during scheduled scans. MSE 2 reports when definitions were checked in addition to when they were updated so that you can be sure it’s working properly if a long time has elapsed between definition updates. The real-time protection functionality offers more fine-grained control. You can now auto-remove quarantined files after a specified interval, though that option is disabled by default. And Microsoft now allows you to opt out of Microsoft SpyNet, the online community that ensures that MSE stays up to date; I don’t recommend doing this for obvious reasons.
K12 Educational Blog 
Hi, I’ve just written this post about computer security:
http://johnager.co.uk/2011/01/16/microsoft-security-essentials/
Best wishes, John.