Today, we have quite a few operating systems. 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. If a program is incorrectly coded, you may see a wrong description in this part of its interface. Menu bar - this part of a program displays menu items and menu options. Some of the most common parts of a menu bar grants access to File commands, Open commands, Save commands, and Print commands. An example of an error in this part of an interface would be if an option was missing or grayed out (lighter in color). bmp - This extension indicates another image file that might have originated from Windows Paint program. .dll - This extension indicates a Dynamic Link Library which may contain additional programming code for software. Many different programs often share Dynamic Link Libraries and you'll find a bunch of them in the Windows/System directory (but don't ever delete them)! Sometimes the links are harmless and attempt to con the reader into volunteering personal information (credit card number), but other times the links attempt to download harmful software onto a computer. Your best protection against computer crimes is your own knowledge. Hopefully the suggestions above will prompt you into taking appropriate action and into protecting your computer with the suggested tools. Nicotine and tar mean certain death when it comes to computer fans, however should you find a need to clean the fan, do so with extreme care. It's quite easy to cause more damage from cleaning so if you're not comfortable with cleaning your PC yourself, take it to a shop for servicing. Otherwise, you can unplug and disassemble the computer to do it yourself. Start comparison shopping and look for the "fastest and biggest." By "fastest and biggest," we mean the computer with the fastest processor, the fastest modem, the biggest memory, and the biggest hard drive capacity. Even if you think that you'll never need the amount of speed or space available on the market today, it's important to have in the event that you truly do need that much in the future.