How to tune display position on external VGA display

[Matteo Riva <muradin@gmail.com>]

I'm using a laptop which I connect to a plasma TV through a VGA
connection.  I can get the display on the plasma to work at the correct
resolution (1360x768) but the image is shifted on the left so that part
of it is hidden and I have a black bar on the right.

My card is a Radeon Mobility 3430. With the ATI proprietary drivers
(which I cannot use now due to display corruption with the latest
version) I can tweak settings with ATI control panel, but now I'm using
the radeon driver and I don't know what I can use to move the display. I
tried xvidtune but all I get is

    Unable to query monitor info

Thanks