AC power adapter

I have a Inspiron all in one desk top error message ac power adapter type and wattage cannot be determined.

System performance is unpredictable. Please connect a Dell 180w ac adapter and restart.

Press F1 key to continue or press button to shutdown.

I have shut the system down and when I hit F1 key nothing happens the above message is still there even after I have shut it completely down.  I have unplug it and left it off over night and today when I pluged back in same above message.

Can anyone help me please?