Cycle the notebook power and battery
1. Turn off the notebook PC.
2. Remove the AC adapter from the notebook.
3. Remove the battery from the notebook PC.
4. Reconnect the AC adapter to the notebook PC.
5. Turn on the notebook PC.
6. Wait until Windows has completely started and the desktop icons appear.
7. Insert the battery into the notebook PC.
Windows will properly detect the battery and the battery should charge normally.
If this does not correct the problem choose one of the following options:
If the battery is older than one year see Purchasing a Replacement Battery
Battery is not older than one year contact HP for a battery replacement.