Today's "older" computers are perfectly capable of accommodating the needs of young PC users, and they're excellent machines for playing educational CDs, small multimedia files, or games downloaded from the Internet. And don't forget the most important role they play in a child's homework-clad life: A simple encyclopedia CD on a used computer makes excellent research tool (not to mention a rather fancy calculator! Understanding Compression What It Is and What's Involved Downloading files from the Internet has always been one of the most popular activities on the Internet - third to sending email and browsing the web. We download files from software libraries, ftp directories, YouTube and Google Video, MP3 sites, and we download files sent to us as email attachments. We described shareware in another article, but because both commercial software and shareware require payment, they're the target of pirates who seek to make these kinds of programs free to use. Depending on their binding legal agreements, licensing typically allows the use of a single program on a single computer. txt - This extension indicates a plain text file that can be opened with Notepad. .wav - This extension indicates a sound file that like the .mp3 file, can be opened with Windows Media Player or Windows Sound Recorder. .Wav files are much larger than .mp3 files. .zip - This extension indicates a Windows archive WinZip file. A powered computer lacking an operating system wouldn't display anything more than a bunch of confusing text messages that describe the computer's boot process. At the very end of this process, the computer looks for an operating system and if not found, it will prompt the user to tell it where it is. When clicked, a small "x" displays inside a box. Similar to the check box, a radio button allows a user to indicate a single choice among many. Problems with radio buttons and check boxes occur when a user makes one choice, but the interface reacts as if the user made many choices (or none at all).