Can't change monitor resolution (openSUSE 11.0, GNOME)

Hi, I bought a Samsung SyncMaster 2243LNX (22 inch) and want to use it as primary display for my laptop. The laptop monitor is supposed to be disabled. But neither I can disable my laptop’s monitor nor I can change the resolution of my SyncMaster (only a part of the screen is shown, right and bottom are missing). I tried to configure with SaX2 but without success. I am using openSUSE 11.0 with GNOME.

When using KDE 4.1 i can change the resolution with a program called “Display”. But after a restart it changes to the old one…

It’s not so important to get this running under KDE 4.1 but under GNOME. Can you help me?

Thanks in advance!