Use the undocumented switch /newmbr to force FDISK to write a new master boot record to the harddisk. This is equal to the switch /mbr of the DOS FDISK command. The switch is documented in the Online Reference of WARP 4.
If FDISK refuses to do something you want it to do (e.g. create or delete a partition), use FDISK in non-interactive mode with parameters. In most cases this helps.
Please be aware that when FDISK is run in non-interactive mode the position (i.e., order) of parameters given on the command line is significant.
Note: Do not rely on the return code of FDISK.