As I have no answers to my question, but some readership, I thought of continuing to talk to myself...
I received by email from Mr. Z on 12 December the above mentioned correction file. Small, it easily unpacked a folder containing a .RAR file which could be opened via Notepad. It proved to be a mission config.sys file that I understands relates to another problem raised by a YAP player.
So I fervently remain wondering: How does this small corrective file install? If it requires a manual installation, into to what folder is it to be placed as an over write?