It attacks computers via distribution - often unknowingly - through email attachments, software downloads, and even some types of advanced web scripting. Viruses that destroy data are known as Trojan horses, viruses that explode their attacks are called bombs, and viruses that duplicate themselves are called worms. Kids will enjoy the ability to play multi-player games and adults will enjoy the ability to blast a single message to everyone at once or maintain a group schedule. Since we're describing a home network that will connect to the Internet, you're strongly advised to install a protective firewall program to thwart Internet viruses, worms, or other damaging spyware code. Although this software does a pretty good job of removing unwanted programs, it can leave some files behind even after a complete uninstall - files which become orphan files. And it's these orphan files that can really clutter up a hard drive and shorten the life of an otherwise, young and robust PC. Even though you may use Windows XP or Vista, batch files can save you tons of time by automatically starting multiple programs and performing different tasks at the single click of a button. They don't require any extensive programming background and they don't need to be encrypted with some weird, expensive compiler. Or maybe that cool new programming language you've been dying to try requires more memory than what your computer currently has. Unless the activities on your computer are restricted to pure textual output (plain text files), your computer is going to get filled with a lot of "stuff" - stuff that can overfill a PC's capacity too much for the computer to function well. " Click the "View" tab and then uncheck the box next to "Hide file extensions for known file types." Click "OK" and you'll notice that the files in Windows Explorer show a dot and group of three letters after their names. That dot and group of three letters is known as an "extension," and the extension explains what kind of file it is.