Thanks to 2e0poz and especially Dean, who spent an hour on the phone with me last night - a case of the nearly blind leading the blind!
Update:
BIOS was set to ECP, now EPP, no change.
Wasn't certain had loaded demo version of Mach3 from the Artsoft site so did that - no change.
Voltages between GND and DIR pins on xyz driver boards all were less than 0.2 or more than 4.8 when active.
Heres something else - I unconfigured the x axis on the ports and pins page (enable off, pins to 0, port to 0) and the x motor STILL grumbles and turns in the same way with no Mach activity!
One other thing, the desktop is a 2.2GHz Compaq Presario. The drivertest program shows a message 'pulsing too fast' but the pulses per sec show as about 15000 to 17000 where I believe 25000 is required, BUT in Mach3 diagnostics page pulses is always within 10 of 25000. These seem to be contradicting messages?
Will have to do some work this morning but unless anyone has inspiration will post motherboard/BOB/cable back to Roy this afternoon (as he has suggested).
So it looks like I'll be back working on motor mounts tonight!
Thanks again
Ian