A firewall is software that checks all data entering and exiting a computer and it then blocks that which doesn't meet specified security criteria (user-defined rules).1 5. Don't click on website links in spam messages. In an effort to obtain personal information, some spammers will send email that asks you to click on a link. It's when these accessories are work requirements or when they're needed to produce works of quality for any other reason that they can become rather expensive. And this expense applies to microphones, digital cameras, PDAs, scanners, video cams, and more. Regardless of cost, it's important to understand that accessories can become "necessities," and that the best time to get them is the moment you buy a new computer. Even though you may use Windows XP or Vista, batch files can save you tons of time by automatically starting multiple programs and performing different tasks at the single click of a button. They don't require any extensive programming background and they don't need to be encrypted with some weird, expensive compiler. Although using a vacuum cleaner seems to make more sense, the strong suction of a vacuum cleaner can actually spark damaging static electricity or dislodge loose cables. You also don't want to use oil-based cleaners. Although Pledge may dust your wooden tables and cabinets to a perfect shine, the oil inside a cleaner like this will erode sensitive computer parts. In its first conception, open source gave birth to the World Wide Web as we know it today. The Internet as a whole is the result of free permission to access the web, use the web, contribute to the web, and share the web with others. But it certainly hasn't stopped there. In the not too distant past, Netscape converted its once commercial version of its Navigator web browser to open source. In fact, by following the simple advice below, you can enjoy the use of your computer to up to five years or more - reserving expenses to simple software upgrades rather then complete and costly hardware upgrades. One of the easiest and least expensive things you can do to extend the life of your computer is to get rid of unnecessary programs, folders, and files.