laptop battery not connecting with a/c adapter

My HP laptop battery recently stopped charging all together on me. I had a previous problem where the outside a/c light would turn on but the windows icon said "Plugged in, not charging." This problem was temporarily fixed by removing the battery and placing it back in. But now it can only run off the battery and the a/c light on the laptop doesnt even turn on and windows gives no notification that the battery is charging in the taskbar. Any ideas what the problem is?

I'm using the dv7 model with windows vista.