I thought most of that double head & triple head stuff was configured in Xorg.Conf. 2 BIOS settings which might affecy things are the "Enable..." for the ginbuilt graphics card, and "Which to check for first" with agp or pci as options. If you are not seeing things, be aware of the bus numbers. lspci -t might help. The bios probably expects to be running windoze which might get very muddled by your box
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