What's the best free AntiVirus software?

Episode 925 (33:13)

Mike from Corona, CA

Leo recommends Microsoft's Security Essentials, which is free.

Mike also noticed that his laptop has slowed down over time. Leo says that over time, Windows can suffer from "bit rot." The easiest way to fix it is to back up his data, then format the hard drive and restore the OS from the recovery disks to the way he got it when he bought it. Then he should make sure to run Windows updates.