Yep agree with Jazz, proper parallel port needed. You can buy a card to plug into a spare PCI port on the desktop PC which will give you a parallel port. Get this sorted first cause you're not going to get anywhere without it. Parallel-USB adapters just do not work for this stuff.

Plenty to choose from on Ebay:

Single Port Printer Parallel LPT Card PCI 810154012848 on eBay!