Sorry, I didn't see that you were using the parallel port. In that case, I suggest you post again for assistance with the parallel port, as I really don't know anything about them.
USB-serial converters "emulate" a serial port. Once you install the correct drivers for the USB-serial converter, the device, whenever it is plugged in, should show up as a serial port under control panel>device manager>ports> comX where X is the com port number.
What exactly are you trying to do? I don't know how popular (or if it's even possbile) to get/emulate a parallel port on a modern computer with USB ports only. You might need to consider that if you plan to move on from your "test laptop".
Also, if you want to do more than just switch relays, you may want to start with a microcontroller kit. If it is really just switching relays, there may be easier ways around this.