Problems with offset desktop on monitor

[Nigel Henry]

I have many distros running on one machine. They are all centralised pretty 
well. Some are a bit smaller than the available area, but I have one Debian 
install which is seriously offset to the right. Only about a quarter inch to 
the right, but enough to obscure the right vertical scrollbar when opening an 
app.

I'm using KDE, and presume that this is built on top of X, so am presuming the 
fix may be with X.

What I'm looking to do is shift the display across to the left  by one quarter 
of an inch so that it's centralised.

Not sure what X.org info stuff is needed here, but on Debian Etch I have.
xorg 1:7.1.0-12
xserver-xorg 1:7.1.0-12

Debian Etch has only recently moved from Xfree86 to Xorg, but this install has 
always been viewed as offset to the right for some reason or other.

Any suggestions as how to to fix this problem will be gratefully received.

Nigel.