Yes to the dud battery particularly if the computer is past its 4th birthday.
Unplug the computer from the wall. Open the box, look for a (usually disk shaped) battery on the mother board. Usually like a large deaf-aid battery. This is usually held in place by a springy blade whic can either be lifted a little or swung to one side.
Pick out the battery and look at the type and manufacturer's code.
Buy a new one from not only a computer store but many other stores from jewellers to supermarkets. When handling a new battery, try to use cotton or latex gloves, they don't like being fondled with sweaty fingers!
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