I have same problem with a Dell Inspiron 1545, after a couple of years the battery wouldn�t charge, went and bought a new battery to no avail, came to the conclusion it is the battery charging circuit or the power pack.
(Some) Dell's will not charge the battery if they think the power pack is inadequate. If you go into the BIOS on booting you'll see what it thinks the power supply is - if it doesn't recognise it then it won't charge.
There's a little chip in the power supply that identifies itself via the slender centre pin on the plug, if that chip is dead, or it's a non-standard PSU, or if the socket connection / electronics on the laptop have died then it won't charge.
I did once change the power socket daughterboard for someone who had bought two new PSUs and a new battery to no avail. It's a design flaw IMHO.
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Phil
MaxDSL - goes as fast as it can and doesn't read the line checker first.
MaxDSL diagnostics