The administrator password has been forgotten and I cannot log in to the VM-100 software.
Delete the VM100DB.vmb file from the database folder (by default, it is stored in C:\Documents and Settings\All Users\Application Data\Brother\VM-100. For Windows Vista, C:ProgramData\Brother\VM-100).
This will delete all your entered data and login details.
Restart the VM-100 software, and the program will prompt you to reconfigure the database path and administrator login details.