discharge them, break the pack up, put them in a PWM charger (one you use to recharge alkalines safely) and cycle on that, do that a few times, then drop them individually onto a concrete floor from 6 feet a couple of times (to break up the crystals inside). i did this to some 10 year old+ ni-mh laptop cells and they came back to life enough to run a small 3w amplifier off for some time.