A computer user only needs to touch various boxes on a screen to control a computer. Sure, the programming behind such technology is extensive and advanced, but to the end user, it makes computer use less intimidating and plain easy. Of course when we talk about operating a computer, we envision more involvement than speaking on the phone or touching things on a screen. Because some programs share common files, errors can also occur when these shared files are not up to date. For instance, let's say that Program A is already installed on a computer and it's working just fine. Then let's say that the user of that computer downloads and installs Program B. Program B uses a file that Program A installed much earlier, but when Program B is run, errors popup. As an example, to load up Microsoft's simple editing program, you had to type the name of the drive that the program was on, the directory that the program was in, and then the name of the program. So if Microsoft Edit was in a directory or folder named "Process," you could start the program by typing, "C:>process\edit. So even though your co-worker may have emailed a funny video, it's no more safe to open than a video downloaded from a complete stranger. Be safe and scan each and every file you download from the Internet or receive through email regardless of where it came from. 4. Create a barrier between your computer and prying eyes. Some of the more popular ones are Windows Vista, Mac OS X, ZETA, IBM, Unix, and Linux. But even still, operating systems have extended onto to non-computer devices such as game consoles, portable music players, and PDAs. Regardless of the device, the operating system installed onto it serves the same purpose across the board: to enable user-to-hardware communication. art - This extension indicates an image file that was compressed with AOL (America Online) technology. Both Internet Explorer and the AOL service software can display this kind of file, however if you don't have AOL installed on your system, Internet Explorer will display it. .avi - This extension indicates a video file playable by most multimedia viewers including Microsoft's Media Player.