In these days of rampant online hacker attacks it is always a good idea to have anti-virus software installed on any computer that will be used to access the internet. While an unprotected PC is almost guaranteed to get a virus sooner rather than later, even with the right software installed it is still possible for a virus program to sneak by. A virus can slow down your PC in a number of ways but even if it isn't slowing your machine down it is still a good idea to check from time to time just to be sure your machine is clean. Watch this video to learn about free antivirus software from Microsoft.