crazybill has a good point... if you have any visuals screen
If you don't (or just wanna change it text based) edit /etc/X11/XFree86.conf
Code:
Section "Monitor"
Identifier "Samsung SyncMaster 753dfx"
HorizSync 30.0 - 71.0
VertRefresh 50.0 - 160.0
EndSection
The Identifier isn't important.. it's freetext.
The HorizSync and VertRefresh is something you'll want to change (probably). Doco on your monitor type should give you the values you want....
If you still have problems.. try running (as root in a console window): X -configure. It should create a XFree86.conf file in the directory you're in (or maybe just in /root). You can either run that file with the command it tells you to test with, or copy the file to /etc/X11 (overwriting the current XFree86.conf).
Good luck
