lol, I forgot about this thread...
I ended up replacing the whole computer. Installing Win7-32bit with an add in PCI-PP card.
I ended up having just as many issues with it, not with crashing, but with losing steps.
Closest I could pinpoint the problem was with the add in PP card. the frequency would
bounce around 10-20hz all the time. It would lose positioning of around 1/2" in about an
hour of run time.
After a few months of fighting, re-wiring the entire machine, I gave up on Mach3 and the PP card.
I picked up a UC-CNC UC300ETH breakout board and software. Haven't lost a single step since.
Super smooth motion, and even faster speeds all around with the new hardware/software setup.
I had a good run with Mach3 but it was time to drop the old hardware. I'll never look back.