How to write to parallel port in winNT by vb ?

I developed a dos program to acces to the parallel port for some hardware control (relay control).
it works on dos,win 9X and win ME but under win NT and win2000
it cant work
Now,I want to rewrite it again in vb6 .How to accsess to the parallel port in vb6 under win NT and win2000.
If I should use a DLL file , where can I find a dll with open code or allowable to use free at all purposes, (that means I can use it in my commecial programs without any fee"