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In windows XP you don't have direct access to ports.
You must write own kernel mode driver that can interfacing directly to ports or use this h**p://www.beyondlogic.org/porttalk/porttalk.htm - this kernel driver allow windows application read/write direct to any port.
My VB program under XP & Win2K which controlling my water heaters & lighting is working well under the activex/IO dll above.
Oh ya... please check whether your computer's parallel port is on ECP mode (bi-directional) which can be used to read or write the port. If it is on SPP mode (one way), then it can write data to port only.