Your Compaq Presario 1240 laptop's CMOS battery is a small battery-operated chip built into your motherboard. It uses a battery not unlike a coin-cell battery in a pocket watch. The CMOS stores information instrumental to the operation of your computer and its software. This includes any boot-up passwords and--most importantly--your computer's date and time settings. If the battery dies, your Compaq laptop will reset your time and date settings each time you restart the laptop. Since the CMOS chip is built into the motherboard, replacing the battery requires completely dismantling your laptop.
Instructions
1. Turn off your computer through your operating system. Disconnect the AC power cable and close the LCD screen. Place the laptop face down and position it so the front opening is facing you.
2. Locate the battery in the bottom left corner of the laptop. Remove the battery's cover by pressing down and sliding it away from the battery compartment. Pull up on the battery pack's locking tab. Grasp the battery and slide it out of the battery compartment.
3. Remove the four Phillips-head screws from along the bottom edge of the laptop's bottom casing. Place the laptop face up, and then open the LCD screen as far as you can. Grasp the palm rest area, tilt it upward and place it face down over the keyboard. Disconnect the ribbon cable from the bottom side of the palm rest.
4. Grasp the keyboard, tilt it upward and place it face down over the laptop's surface. Disconnect the keyboard's ribbon cable from its connector on the motherboard. Remove the keyboard from the laptop and set it aside.
5. Locate the heatspreader plate revealed by the keyboard. The heatspreader is a thin metal plate covering the motherboard. Remove its two retaining Phillips-head screws, and then remove it from the laptop. This reveals the processor chip.
6. Locate the CMOS coin-cell battery next to the processor chip. Grasp the battery and remove it from its compartment.
7. Repeat this procedure in reverse to install the replacement CMOS battery and reassemble the laptop.
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