By John Martinsen You may not have realized your computer, much like a car or other piece of machinery, needs regular maintenance in order to operate in a reliable and efficient manner. We're not talking oil changes or engine tune-ups. Most of the work can be accomplished with a few simple keystrokes, and some tasks can even be scheduled to run automatically. If you're willing to put in a little time and effort for this kind of preventive maintenance, you might save yourself a major headache and some potentially expensive problems down the road.

This month, we'll look at some basic maintenance tasks - how to keep your computer clean and your hard disk drive working on its best behavior.

Keep It Tidy Computers don't like dust. At least once every couple of weeks you need to dust off the equipment. A dry rag will usually do the trick. But if you need to use a cleaning agent, make sure you use one specifically designed for sensitive electronic equipment.

Your keyboard and mouse may become unresponsive or unreliable if they're constantly exposed to a dusty environment. If the work area your computer is set up in is particularly dusty, you may want to invest in a keyboard cover. Some covers are designed to protect your equipment only when it isn't being used, while others fit snugly over the individual keys and are intended for permanent protection even as you work on the computer. Most computer stores and office supply dealers keep these products in stock.

Each month, clean out the mouse. If you turn the device upside down, there's usually a small panel underneath that can be slid open. Take out the rubber ball inside and wipe it off using a moist cloth. Inside the mouse you will see two or three small rollers or wheels. These gradually build up a layer of dirt and grime and need to be cleaned off as well. Use your finger or a pair of tweezers to get rid of the buildup, then dry off the rubber ball and replace it along with the plastic panel.

Hard Drive Housekeeping No component in your computer is busier than your hard disk drive, which retrieves and stores data every time you perform an operation. As a result, this delicate piece of equipment needs special attention and care.

Both Microsoft Windows 95 and the Apple Macintosh operating systems come with a set of tools that help you take care of the hard drive. The two most important tools are the ones that let you check the hard drive for errors and optimize the way information is stored.

In Windows 95, the troubleshooting program is called Scan Disk. You access it through the "Start Menu," where it's listed under: Programs/Accessor-ies/System Tools. Normally, it's enough to run the "Standard" test on your hard drive, perhaps once every two weeks or so.

The "Thorough" test is more useful if you're already experiencing problems when accessing files, or if you suspect for some other reason that there might be a problem with your hard drive.

The Apple Macintosh counterpart to Scan Disk is called Disk First Aid, and it operates in much the same way as described above. The default location for Disk First Aid is the "Utilities" folder on your system disk.

Defragment The Hard Drive While Scan Disk and Disk First Aid take care of potential problems with the data on your hard drive, Windows 95's "Disk Defragmenter" serves to speed up how you access your data.

Each time you store something on a hard drive, the program or file isn't stored as a single entity. It's split into data segments that are stored in different locations throughout the hard drive.

As you store more data on the hard drive, and as you open and save files repeatedly, this fragmentation becomes more and more severe. This in turn slows down the rate at which files and programs open when you request it, as the operating system repeatedly accesses the hard drive's "road map," or file allocation table, to find out how the various segments of the file are stored.

The Disk Defragmenter rearranges how your data is stored, moving file pieces that belong together into continuous areas on the hard drive. As a result, the operating system doesn't need to call on the "roadmap" quite as many times when opening a file, and you'll see an increase in speed when you work with complex programs and data files.

There are a number of Macintosh disk defragmenter programs offered, but must be purchased separately from the operating system. If you have access to the Internet, look for a free or shareware defragmenter program on sites such as www.download.com Be aware that a disk defragmenter takes a long time to finish, especially if you haven't used it for a while. Run it about every two weeks and it should finish the job in a half hour or less.