Compaq Portable - BIOS revision B
COMPAQ Portable
Revison B of the motherboard BIOS does not support BIOS expansion ROM's (as found on cards like the EGA and XT-class hard disk controllers).
It is valid to upgrade the BIOS revision to C.
A ROM image that can be used to create an EPROM of BIOS revision C, is at here.
If you are unable to create the EPROM yourself, note that some people/companies that can create an EPROM for you are shown at here.
Note that per here, revision C of the BIOS treats the motherboard switches differently to revision B.