Yep, those legs are spot welded to the battery, so remove it by resoldering from the motherboard, or carefully cutting the 3 legs close to the motherboard.
Another good alternative battery is to use a 3.6V Ni-MH cordless phone battery. They're cheap and easy to get. Just cut of the 2 pin plug, and solder the two wires to the points where the old battery used to be.
Watch the polarity.
On the A3000, the black wire goes to the single hole (nearest the monitor jack) and the red wire connects to either of the two side-by-side holes.
