I'm having trouble getting the right screen resolution to work for an external monitor in a Sony Vaio laptop (VGN-TZ15GN, though this is the Latin American model number, which I think is different in other parts of the world), which comes with an Intel graphics card.

The external monitor is a Viewsonic VG2030 WM, and the suggested resolution is 1680x1050. With Gutsy it was possible to get this resolution by modifying the xorg.conf file, but that part of the file isn't there any more in Hardy, and the maximum resolution I can set in the System -> Preferences -> Screen Resolution is 1280x768.

Any ideas?