17" monitor thinks it's a 15 inch?

[superwomble cyberdude com]

Have a strange screen problem in X, and have never seen this problem
mentioned here.

Have installed 5.2 many times on machines with brand name nd non brand
name monitors ranging 14,15 & 17 inches. Xfree always installs properly
on the screen, never needing xvidtune for fine -tuning. 

I have just purchased a PAnasonic PanasyncE70, a very new 17" model I
believe. When installing 5.1 using this monitor, the desktop is placed
squarely in the screen, with a 1.5 cm black line of unused real estate
evenly around the border of the desktop. If you shrunk this monitor down
to 15", I guess it would be a perfect fit. Xvidtune cannot  resolve this
problem.

Does anyone have any advice? Talk about a waste of space!