Add a command line to the fm 2008 shortcut specifying the correct resolution of your montitor...
1st right click the desktop and select - Properties
then click the settings tab and find the resolution of your screen, as someone previously posted the resolutions you stated sound wrong tbh...
then right click the fm 2008 shortcut icon in the start menu...select properties..
where it says Target edit the command so it reads
"C

Program Files\Sports Interactive\Football Manager 2008\fm.exe" -fullscreen_width=**** -fullscreen_height=****
**** being your screen resolution ie width 1680 height 1050
I'm sure someone else has posted it before anyway hope it helps