If your Windows 2000 laptop can install 2 batteries, Windows 2000 may NOT run the low or Critical battery alarm, as set in Control Panel / Power Options / Alarms.
The problem is caused by Windows 2000 improperly calculating the remaining time when 2 batteries are installed, and AC power is unplugged.
The formula for calculating remaining time is:
RemainingTime\[h\] = RemainingCapacity\[mAh\] / PresentRate\[mA\]
NOTE: Remaining time in hours is equal to Remaining Capacity in mili-ampere hours divided by the Present Rate of battery power consumption in mili-amperes.
With 2 batteries installed, the formula should be:
RemainingTime\[h\] = (RC1 + RC2) / (PR1 + PR2)
RC1 is the remaing capacity of the first battery.
RC2 is the remaining capacity of the second battery.
PR1 is the present rate of the first battery.
PR2 is the present rate of the second battery.
Unfortuneatly, Windows 2000 is using:
RemainingTime\[h\] = (RC1 + RC2) / PR1
This can result in a sudden loss of power.
I suggest that you either increase the power level percentage in an effort to compensate, or to be safe, use one battery and have the critical alarm Hibernate your laptop so you can replace the battery.