Umm laptop wont charge?

I have an HP laptop. It says its charging and it stays on while in the charger, but when I take it out it has the same amount of battery as before. What to do? Why is it doing this?

HP G4-1010US Notebook Intel Pentium P6200(2.13GHz) 14" 4GB Memory 320GB HDD 7200rpm DVD Super Multi Intel HD Graphics

HP G72-B50US NoteBook Intel Pentium dual-core P6100(2.00GHz) 17.3" 4GB Memory 500GB HDD 5400rpm DVD Super Multi Intel HD Graphics

HP ProBook 6560b Notebook Intel Core i5 2410M(2.30GHz) 15.6" 4GB Memory DDR3 1333 320GB HDD 7200rpm DVD Super Multi Intel HD Graphics 3000

HP ProBook 6455b NoteBook AMD Phenom II Dual-Core N660(3.0GHz) 14" 4GB Memory DDR3 1333 320GB HDD 7200rpm DVD Super Multi ATI Radeon HD 4250