Thinkpad 310ED won't stop beeping with Win 98?

My IBM Thinkpad 310ED came originally with Windows 95. I just installed
Windows 98 (Second Edition). It now beeps every ten seconds so. Sounds
like the battery low warning, though I disabled all the battery warnings
in Windows 98. The warnings stop when I connect the wall charger/power
supply.

The battery is full and I can monitor its status with the battery
indicator that's built-in to the BIOS.

I have not installed any of the IBM utilities for Windows 98.

Does anyone know how to stop the warning beeps?

Thanks for your help.