DELL Latitude D510 not charging

I bought a DELL Latitude D510 about 2 years ago. I didnt have much problem with it. But now theres a problem. It wont charge. It was charging fine before but it is not charging now. when i connect the AC adapter to the power the gree light on the power turns on but the battery keeps on discharging. Is it just the end of Battery charging span or can be more dangerous problem..Please help me with this problem.

 

Thanks for any help u provide.