FUJITSU DYNAMO 640FE - Manual (Page 21)

1.18
3.6 Formatting an MO Disk
Many new MO disks may not be formatted. If your MO disk is not formatted,
you will need to format the MO disk before use.
for PC users
1) Using Explorer, open My Computer.
2) Right-click the Removable Disk icon corresponding to the DynaMO
and select [Format...].