This might be a good ideal to ensure one does not have a sneaky root kit or other bot net bug running on your computer...
http://www.microsoft.com/security/sc...s/default.aspx
Thanks Kelly, but the bottom line in that Description holds the key. If one is not running Security Essentials and doing an automatic daily update and scan, then one is nuts.
Security Essentials, has been consistently shown to be the most effective protection out there. Seems a no brain-er to me. You can define/limit the amount of CPU time that scan hogs, so it is pretty unobtrusive. I have mine set for "about 9:00am" and never notice it going to work and doing it's job.
Now, the Windows Firewall is another (sloppy) thing entirely, so I use ZoneAlarm or Comodo. All free stuff, too.