I’ve installed on a presario laptop (s3 k twister g card) which has a 1024x768 max resolution. However the display shows 800x600 and the screen properties has no 1024x768 option. Is there any way to add such an option? (The system is fully updated)
Try running sax2 from the desktop. Launch it from the main menu or via console with sax2. Enter your root password when prompted. From here, you can select the monitor type. All going well, this will allow you to set the correct resolution.
There are other potential xorg issues with some graphics chipsets that can cause resolution problems, so if this is the case, post your xorg.conf contents.