Man, I'm talking to myself!
Sorry for this, but I got stuck with the disk.rom.
I have 3 or 4 different versions but none of them seem to load. Dropping out to the command line, I get:
C:\Progra~1\mess087b>mess msx -cart disk.rom
Driver reports load for cartridge device failed
Ensure image is valid and exists and (if needed) can be created
Unable to initialize machine emulation
Looking at this bug report here: http://bugzilla.mess.org/show_bug.cgi?id=460
and these pages here: http://www.msxnet.org/mess/news http://www.msx.org/forumtopic1487.html
they seem to suggest I need a disk.rom which is listed in msx.crc (where's this file??).
I can't seem to find such a disk.rom file in what I think is my complete bios.rom set (the only disk.rom is in the msx2.zip file and that doesn't work). Searching the archives, does come up with some discussion of this topic but nothing which has helped me work out where to start looking for a new disk ROM ...