I would pull the batteries out of any computer that you are not regularly using. I have lost two PM 6100's because the batteries exploded destroying the motherboards, power supply, and cases.
If the battery is registering under 3.3v, I wouldn't hesitate to clip it. If it is still good then I would check the battery and start the computer up regularly. A couple weeks ago I clipped the battery in one of my SE's and soldered in a new battery holder.