Turns out, the problem has nothing to do with PBP/XP directly. Following a long and exhausting time plugging away at the problem, I realized that any program that attempted to execute command.com would crash the computer. Therefore, command.com was the true culprit, or some byproduct thereof.

All in all, I think it was a memory problem...

To make a long one short, I reinstalled Win-XP and everything works as expected!

Thanks, Eric