If you have an old DOS or Windows legacy application (or even a newer Windows application) that will only print on HP LaserJet printers that support PCL, you probably cannot print from this application to most of the new printers on the market today, unless it is a PCL printer. Even HP is selling fewer printers with PCL included.
JetPCL Print Filter (JPF) or JetPCL Document Capture (JDC) can usually help in this situation. JPF can attach to most traditional non-PCL print drivers and enable them to support PCL data send to them by the legacy app. JDC offers a separate print driver install designed to convert your applicaton PCL data and send the results to the printer you choose. JDC can also capture print output to an electronic document formats so that you can, not only print, but also, email your documents.