vicomputer, wait five seconds after turning off thecomputer before removing the memory module ordisconnecting the device to help avoid possible dam-age to the system board.• Before you clean your computer, turn it off, unplug itfrom its power source, and remove the battery.• Clean your computer with a soft cloth dampenedwith water rather than with liquid or aerosolcleaners.Clean the display with a soft, clean cloth and com-mercial window cleaner that does not contain wax orabrasives. Apply the cleaner to the cloth; then strokethe cloth across the display in one direction, movingfrom the top of the display to the bottom. If the dis-play contains grease or some other contaminant, useisopropyl alcohol instead of commercial windowcleaner.• If your computer gets wet or is damaged, follow theprocedures described in Chapter 3, “TroubleshootingYour Computer.” If, after following these procedures,you confirm that your computer is not operating prop-erly, contact Dell Computer Corporation. (SeeChapter 5, “Getting Help,” for the appropriate tele-phone number.)Ergonomic Computing HabitsFor comfort and efficiency, observe the following ergo-nomic guidelines when setting up and using yourcomputer:• Position your computer directly in front of you asyou work.• Adjust the tilt of the computer’s display, its contrastand/or brightness settings, and the lighting aroundyou (such as overhead lights, desk lamps, and thecurtains or blinds on nearby windows) to minimizereflections and glare on the display.• When using an external monitor with your computer,set the monitor at a comfortable viewing distance(usually 510 to 610 millimeters [20 to 24 inches]from your eyes). Make sure the monitor screen is ateye level or slightly lower when you are sitting infront of the monitor.• Use a chair that provides good lower back support.• Keep your forearms horizontal with your wrists in aneutral, comfortable position while using the key-board, trackball, or external mouse.• Always use the palmrest with the keyboard or track-ball. Leave space to rest your hands when using anexternal mouse.• Let your upper arms hang naturally at your sides.• Sit erect with your feet resting on the floor and yourthighs level.• When sitting, make sure the weight of your legs is onyour feet and not on the front of your chair seat.Adjust your chair’s height or use a footrest, if neces-sary, to maintain proper posture.• Vary your work activities. Try to organize your workso that you do not have to type for extended periodswithout stopping. When you stop typing, try to dothings that use both hands.When Removing or InstallingMemory ModulesBefore removing or installing memory modules, performthe following steps in the sequence indicated.1. Turn off your computer and any attachedperipherals.WARNING: Improper or prolonged keyboard usemay result in injury.CAUTION: The only time you should ever accessthe inside of your computer is when you are install-ing memory modules. Wait five seconds afterturning off the computer before disconnecting aperipheral device or removing a memory module tohelp prevent possible damage to the system board.