Have you checked with everest to see what resolution your monitor supports ???
As I can see from the manual for your computer, your display supports:
Display
15.4-inch TFT WXGA / 1280 x 800 pixel non-glare display, (glare optional) x
Your Graphics Card should support:
Max. resolution for external displays
Up to 1920 x 1440 / true color / 60 Hz
The driver from the SiS manufacturers site supports only XP, so the only driver you can use is the one provided by FSC.
Select your model and download it from here
http://support.fujitsu-siemens.com/com/ ... loads.html