I have a Dell Latitude D610 laptop and the charger that i use doesnt work. It worked about a week ago, but now everytime I plug it in, it doesnt charge, the green light that is on the power unit doesnt light up, and it makes this tiny beeping noise. Anyone know why its not working and how to get it to work?

Its a gateway laptop and runnig vista. It used to be able to connect to a network but not anymore help please