>Dear Cristóbal,
>
>Maybe it's OS problem. Check this :-
>
>A couple of years back, Win3.11, Panasonic 3626, bits and pieces of the line being printed is "brought-forward" (or up), i.e. the words "HELLO WORLD" are filled with white dots, and the those missing pieces goes down.
>
>Guess what, we changed the driver for the VGA card, and the problem disappeared.
>

It's not surprising at all; both the printer and the video driver interact, since both provide services to and rely on common routines from a layer called the GDI, or Graphical Device Interface. Windows has been plagued by certain driver interactions between the print and video layers since day one.

In this case, it's unlikely that it's a driver interaction - HP simply has a rep for releasing buggy drivers, going back to the wee early days of Win3.x, and I hate to say it, in the past couple of years, their rep has gotten worse!