but by just fitting a Nvidia AGP or PCi Express card this is not overclocking. For some reason why does the motherboard not work well with a dedicated graphics card. Is it because of the AGP limit with the Onboard VGA ?
The graphics card is irrelevant as far as the answers are concerned - the responses are only relating to the processor type and overclocking ability. There's nothing there to suggest it doesn't work well with a dedicated card.