I have a Dell 1501 laptop, only a few months old. My daughter was using it on battery power and it went completely flat. Now if I boot it either with battery power or AC I get a message "Battery not recognised" and it won't continue to boot unless I press F12 and run the Broadcom boot. Although this doesn't actually do anything, it does allow the system to continue booting. I can't find anything wrong with the battery or the AC adapter.