I just bought an external monitor for my laptop (Asus VH242H) but cannot set its resolution to anything higher than 1600x900. I tried both from System/Administration/Monitors and the ATI Catalyst Control Center. There was a CD that came with the monitor but it only contains a Windows installer.
According to the monitor's specifications:
23.6” 16:9 widescreen with 1920×1080 resolution enables borderless Full HD 1080p full-screen video display.
My graphic card is an ATI Mobility Radeon HD 4670 and the monitor is currently connected to my laptop with a VGA cable.
How can I set my external monitor to its maximum resolution?