Dell Laptop Battery Problem 4 green 1 amber light flashes

Dell Inspiron 5100 battery light flashes 4 x green 1 x amber. Control Panel Power Options shows no battery installed. Works OK with AC Adapter. Tried two AC adapters. Tried two batteries. Same results. Windows XP Home Why would battery not be recognized?

I don't have an answer for you, but to give you something to check while waiting on someone who may have a more specific answer, Dell have put out recalls on certain battery's known to have a problem, I suggest checking you're battery is not one of those affected, you can do this at the following link:-
http://www.dellbatteryprogram.com/

Apart from that it must either be a bad battery, or the circuitry involved with charging etc has become faulty, but whatever the fault, I fear it wont be sorted without taking it to a shop capable of such a service, unless a new battery is the cure, but you mention a couple of battery's so I fear the issue may be deeper than just a battery, but still check you're battery's are not affected under the recall, hope this gets you started anyway