Yeah, this laptop IS a couple years old, and the battery may be finished-BUT for the fact that sometimes it won't run off AC power at all even when the thing is plugged in-it has to be set just right, and sometimes "just right" has to be adjusted.
Personally I think it has something to do with my internal hardware-it's heated up fairly badly before because of some stupidity.
I have no idea what would happen if I pulled my battery.
As for what Ktabic and Joe have said, I have looked into the computer plug and I haven't ever seen any kind of pin, and I know this is a proper adapter. It IS a Dell adapter and over 65W like it said it needs.
I guess it's proper of me to actually list my error message:
"The AC power type cannot be determined. Your system will run slower and your battery will not charge. Please connect a Dell 65W or higher adapter for optimal system function."
I suppose, though, this happens quite often with Dell laptops, on sites I've read numerous people have had this problem. One person is even claiming a class action suit against Dell over it.....