There are three possibilities in descending order of probability: The DC plug on the adapter is damaged (check the center pin to make sure it's straight and undamaged), The DC jack in the system is damaged, or The charge circuit on the system board is bad. Replace the adapter first, jack second -- if neither of the first two produces the result of a recognized adapter, the charge circuit is the issue and the mainboard will need to be replaced.  
[IMAGE]   Whenever I turn on my computer an error shows up saying “Alert! The PC power adapter wattage and type cannot be determined. The battery may not charge. The system will adjust the performance to match the power available.” It lets me turn on the computer after but the battery doesn’t charge, the computer also runs very slowly. I’ve tried just blowing into the port and such, but nothing is working, am I going to need a new charger?
Alert! The PC power adapter wattage and type cannot be determined.”