Follow these steps if you need to set up a USB printer on LPT1 in order to print using legacy DOS programs:
1) Install printer on USB port and test printing from Windows programs
No sense even starting if you can't print from Windows
2) Control Panel --> Printers
All of your printers should be listed, including your printer that is installed on USB port.
3) Right-Click on the name of the USB printer that you want to set up for DOS printing and choose "Properties" from the pop-up context menu.
4) Click on the "Ports" Tab at the top of the Printer Properties Window.
5) Make a note of the exact name of your USB Port.
6) Select the "Enable Printer Pooling" checkbox. i.e. be sure that the box is checked.
7) Scroll up and/or down through all of your listed ports and click the "LPT1" port to place a checkmark in it. Note: You should now have both LPT1 and USB ports selected
8) Click "Apply" and "Ok".
You should now be able to print from your DOS program to the USB printer, the above steps essentially trick Windows to act as though the USB printer is connected to LPT1.
Printfil is a utility that is available for $49, www.printfil.com for more information.