Be Excellent To Each Other

Battery wouldnt hold charge, but it still worked off mains power...
I didnt really care as long as it turned on.

Kalmar why won't you fix my laptop if you can?

I'm guessing, as you used your laptop as a desktop, that you always had the laptop connected to the mains power when in use?
For future reference (if you ever get a new laptop) laptop batteries 'learn' how to charge efficiently. If you don't run the laptop from the battery between charges the battery will hold less and less charge and eventually die.

Hey everybody! Is this true? If so, I have some unplugging to do...

Batteries with fuel gauge (laptops) should be calibrated by applying a deliberate full discharge once every 30 charges. Running the pack down in the equipment does this. If ignored, the fuel gauge will become increasingly less accurate and in some cases cut off the device prematurely.

A lithium-ion battery provides 300-500 discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery. There is no concern of memory when applying unscheduled charges.

Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as "digital memory". Here is the reason: Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery's state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate