How to remove power on / bios password Compaq NC6400 and Nc8230

Usually when you want to reset bios password you have to remove bios battery, but this Compaq NC series have hidden this battery under the keyboard. First you have to remove battery and 3 screws, open the keyboard, unplug battery wire, boot computer again (without battery and without bios battery), then turn computer off and replace batteries and keyboard.