Weird parallel port issue

I've just powered up my new CNC setup and can't explain a bizzare
event. I'm running Windows XP. My X and Z axis have no problem. I
have the step line of my Y axis drive connected (through a breakout
card) to parallel port pin 4 (and the Y direction is pin 5). When XP
boots to its welcome screen, my Y axis stepper turns at a slow rate
of speed. It continues to turn until I launch MACH2 (alpha) at which
point it stops turning (and works as expected with the software). It
will stay stopped even when I exit MACH2. I have a fourth axis on
the breakout board that I can try, but I'd really like to know if
anyone has a clue as to what is happening as I'd hate to waste the
potential of the other axis.

Thanks for all your previous input.

Regards,
Jeff