Receipt Printers - No Two Alike?

A frustrating day to say the least. Had a POS terminal that would not print receipts. Fixed some windows errors, updated the service pack and various patches, reinstalled the primary application - still no joy. Installed a new printer driver (A generic "Vendor Thermal Printer" driver) and played around with the virtual USB port settings. And then, finally, it started printing! I don't even know what little check box or setting made it work! We compared a second working machine - same HP box, same POSx r500x printer, USB connections, same application, same Epson emulation - yet different drivers and configuration settings!! Grrrrrrrrrrrrrr. Thanks, JS, for help in getting the thing working.