Siemens Nixdorf PCD-4ND, Phoenix 1.03

[pcd4nd]

I know this is maybe an unusual request in this forum - an unlock request for an vintage laptop from the 90's. I would like to disable the internal sound chip (ESS AudioDrive ES1688F) of the PCD-4ND to use a Soundblaster compatible ISA-card in the docking-station. The PCD-4ND has the ancient Phoenix BIOS A486 Version 1.03 REV-F3Q42/3H13.

In the Phoenix BIOS "System Setup" menu is a field "Audio Device:". I can not choose any options for "Audio Device:" as I can on other items (see attached image) in the "System Setup". I would guess that Siemens Nixdorf has castrated the BIOS.

general info to the PCD-4ND: http://boginjr.com/electronics/old/pcd-4nd/
BIOS for PCD-4ND available at: http://support.ts.fujitsu.com/Download/