I would offer an opinion!
From your statements;<1>we cannot get the START.com or INIT.com programs to work. START returns "RTX not ready", but then says the library has been installed permanently(?). <2>INIT returns "RTX Cannot be initialized" with an error code of $11 (COMMS_NOT_READY) but we did see $20 (NO_RESPONSE) at one point. We have tried running the programs under Win XP command window, and also from a DOS boot disk with the same result.
I would address the communication error,<2>, because, if your can not communicate, no file will help you<1>, and it may appear that the program running under the windows or dos is not working.
The only alternative I see, is that, find a similar program on the internet as work form that information; or,
take out the ROM, read it, and try to debug/analyze the program to find the problem. If the ROM has
been corrupted, no amount of work on the system will help. If you could obtain a master ROM file from
somewhere, reprogram one, then put that into your system board, that may work. The last ditch effort is
the ROM slot with your own program, and force the robot to run your dedicated program.
Alot of work, either way, good luck. Keep me posted...............