I tested both ATI HD2400 and NVIDIA G210 PCI-E VGA card on C2G41 with Windows XP and 7, but cannot have dual display with onboard VGA. Can you update BIOS to fix the problem?
Please ask technical support for BIOS released after 7/13/2011, which fixed the problem. After update BIOS, go to Advanced => Advanced Chipset Control => North Bridge Configuration, and set Boots Graphic Adapter Priority to PEG/IGD. It can only support extended display; clone or twin are not supported.