P had installed a new POS system on a Win7 Lenovo netbook and was having trouble printing to the USB receipt printer. It was printing, but leaving a lot of blank space at the top before printing and cutting the receipt. Finally fixed it by going to the printer properties, and in the paper settings, choosing 'Conserve paper' 'Top and Bottom'. The font is also different from the one seen in his other POS, which runs Linux. Probably because the Linux machine is printing to a driver similar to Generic Text. Trying Generic Text driver on the Win7 box gave the "correct" font, but the layout was awry. Probably an issue with paper settings for that driver, too. Anyway, since the smaller font is OK, he'll probably go with the Epson driver.
Edit: P adds:
Finally was able to get this work with correct font size.
Suggestion from this forum post.
Epsons POS website had the latest virtual COM port software which works for Windows 7: TM Virtual Port Driver Ver.5.00aE . Assigned the printer to COM1 through the software and changed the openbravo pos settings to Printer: epson -> Serial -> COM1