I have a Inspiron 1545 with the same problem. HAD i mean. I just ordered a new power supply from Hong Kong, dealextreme.com. It Costs 13 usd and free shipping. It takes a while to get stuff from them , but it will show up. Plugged it in, got a message at startup that pc dont recognize the supply, pressed F1 and it started, AND its charging again, yeaaaah :) This is the link for the one i bought... :
http://www.dealextreme.com/p/replacement-power-supply-adapter-for-dell-laptop-7-4-x-5-0mm-108193?item=2 You need a different supply, but i know they have that one to...
Not expensive, so worth a try....