I need my old LPT1

Recently a customer call me asking me to solve a problem: his new printers does not print from accounting network system. After check the new equipment I discovered that he has a old system which send the printing to lpt1. But the new equipment (sixCompaq evo D510 slim whithout expansion slot for a new card) does not have parallel port but usb. I need the old lpt1 or an alternative so that the old software can print in the new machines using the usb but being recognized as lpt1. What solutiondo you suggest?