Output to I/O port under NT 4.0

Answer:
Well, the world changed between NT and previous MS operating systems. In particular, application programs (running at ring 3) have been forbidden to use direct hardware access (level 0). You have two choices. One, you can dig into the DDK and write your own device driver, but this is no task for the faint-at-heart. The easier way is to buy one of the shareware or commercial applications that have already done this. I list two below, but there are probably more out there.

BlueWater Systems WinRT OCX—32-bit control (port I/O, physical memory access, and interupt handling—Win95 and NT).

TinyPort, shareware by Manfred Keul (read and write I/O ports under NT).