I have a problem with an Hp Compaq nx6325. One day it started making a high pitched noise that comes on and off every other second. Upon looking at it closely I noticed the charging battery light was turning on and off. In addition, the screen kept dimming and brightening. When I unplugged the power cable the noise and flashing stopped. Likewise when I plugged in the power cable and removed the battery it worked. The only problem was that the laptop would not charge the battery and it would not work properly when both the battery and the power cord were plugged in. I disassembled the laptop and found that the internal power supply (the slot the power cord plugs into and the source of the high pitched noise) was a part of the motherboard. After a few months another identical laptop is having the same problem. Since they are both out of warranty and my company has 48 more of these, what can I do to repair this and how can I prevent it?