When my FM TOWNS II Fresh・E suddenly refused to boot from HDD and Towns OS (from CD) didn’t show the HDD anymore, my first thought was that the HDD has finally given up. It had sounded like an airplane engine lately (and still does). Then I noticed that date/time settings were lost too, meaning it was probably related to the BIOS battery. To access or replace the battery (3V CR2450), the whole unit needs to be disassembled.