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. Those errors are the result of Program B attempting to use an outdated (shared) file that was installed by Program A. mid - This extension indicates a sound file created with a Musical Instrument Digital Interface. Windows Media Player will open and run these files, however they don't sound like normal .wav or .mp3 files (described later). .Mid files are designed to product synthetic sounds using a computer's sound card. Decompressing Files Assuming that you have Winzip or StuffIt installed on your computer, you can access the files archived inside a .zip or .sit file by simply double-clicking the archive (a file ending in a .zip or .sit extension). Double-clicking one of these kinds of files will open up a window that displays the contents of the archive. The only way to get an MS-DOS computer to do something was to type a command at this prompt and if you can imagine, it was a rather cumbersome way to use a computer. 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. On one hand, it affords us quick and easy access to numerous conveniences such as bank statements, favorite shopping centers, school and health records, and more. On the other hand, it can also grant the same access to those who aren't supposed to get it. Although it's a rare occurrence, hacking has become the biggest criminal nuisance in computer history. Be aware however, that because shareware is not commercial software, you may not experience a full program the way you would if you bought the software out of a box. Shareware may or may not be limited - meaning that some functions may not be available to you until the program is paid for. These limitations are often small and don't interfere with the way its full version operations.