"Li- Ion chemistry batteries can occasionally be brought back to life, however it is not without some risk. Li-Ion or Li-Poly chemistry has threshold voltages that the batteries must be kept within, you can do some research on this battery chemistry for model aircraft use and get more and better info than space will allow here. You will need to 'cycle' your battery to bring the capacity back to almost normal. You will need to discharge the battery out of the laptop via jumper connectors, and recharge while MONITORING the battery a number of times. You can discharge through the laptop, but you wont be able to monitor the voltage or control the rate of discharge (risky). Finding a hobbyist with the proper chargers to charge and discharge Li-xx chemistry batteries is the safest way to go, as you will charge outside the laptop and be safer in the event of fire. Do not under any circumstance dismantle the battery housing, you risk causing a fire due to puncturing the membrane and shorting the cells internally. The batteries are great, the technology buried in your laptops' charge circuitry does a fine job of masking the inherent danger of fire."
For one laptop of mine, a replacement battery cost $200 list. A new laptop cost me $600. It seemed like a better deal. Consider that for the cost of battery you can buy a substantial chunk of a low-end laptop or most of a netbook.
