That's a rather generic question. You get the standard generic answer.
I had this new motherboard which don't have a parallel printer port so I install pci printer port which assigned as lpt3. I'm having hard times configuring it, the program I'm using is purely DOS. Thanks
Are you running XP and a DOS type program from within, or are you starting the computer with a DOS disk and running pure DOS? I'll guess you are running a DOS window from XP.
Start>Control Panel>System>Hardware>Device Manager>Ports (Com & LPT)
Click the little plus sign in front of this location.
Right-click on your parallel port card and select Properties, then port settings. Under LPT port number, choose LPT1.
You may need to re-start the computer to computer the change.