Parallel Port Access

I´m developing a software that send signals to the parallel port, but i actually discovered that windows XP blocks my attempts, how can i send the signals without being stopped? I already tried dll´s that say that with them i can access the LPT but i couldn´t, it simply showed no result, no errors no efects example of a dll: http://www.logix4u.net/inpout32.htm

OS: Windows XP Professional Service Pack 2
COMPILER: MS VC 2005

http://www.lvr.com/parport.htm
Did you try this as a normal user, or as admin. Newer operating systems can be pretty picky about letting programs access the hardware directly.

i tried that as a normal user with admin privilegies, and i already saw that website, in linux i was able to access the LPT but not in windows.