TechMage:
I'm flattered, thanks.
(But you get a

just in case you were being facetious

).
Just for the record, it's not technically a coding problem, it's a lack-of-documentation problem
Cryo:
Thanks too - that's what I was looking at, but I'm not willing (or able) to throw money at Compaq for this

If there's somebody with a membership that could forward my enquiry, I'd be eternally grateful. I'm pretty sure that I need somebody with a membership rather than a "subscription".
Ho hum, another interesting project might be going to the wall

I might try and hack the interrupt vector table to work out what it's currently doing with the interrupt. Looks like I'm in for more low-level hackery this evening then.
Cheers,
Ref.
(unless our parent company is part of the Compaq Solutions Alliance thing already, in which case I might be in luck... hrmmm).