As you can imagine, the cumbersome process of switching from floppy to floppy prompted the birth of the operating system. An operating system is a software program that controls how the computer's hardware (and installed software) works. It manages the activity of every component and then displays that activity as a user-friendly interface (GUI). Chances are, Grandma isn't ever going to shell out the bucks to buy the latest computer on the market, nor is she going to know how to use it once she gets it. What Grandma doesn't realize however is that a used computer is an excellent training tool that she can use to prepare herself for something "better" in the future. Install an anti-virus/anti-spyware program. Anti-virus/anti-spyware software will stop malicious code from downloading and installing onto your computer while you peruse the Internet. Known as viruses, worms, or spyware, this malicious code can destroy important files and render your computer good for only one thing: sending sensitive data back to the server of an identity thief. One of those advantages is its cost. On the whole, shareware is generally cheaper than commercial software. But don't misinterpret the cost. With shareware, cheap does not equal low-quality and there are plenty of examples that prove shareware often outperforms the quality of commercial software time and time again. But without seeing the extension, you wouldn't know it unless you double-clicked on it. The following list defines some of the most common extensions that you'll find on your computer. .au - This extension indicates a sound file. Most sound players will load up and play this kind of file. .art - This extension indicates an image file that was compressed with AOL (America Online) technology. These extras aren't included with "what comes out of the box," and the only way to get them is to accessorize. To illustrate the importance of accessorizing, we like to use the "plain dough" analogy. Let's say that a brand new computer is a batch of plain dough - waiting to be flavored and baked into something useful.