You need to enter the bios and disable the onboard video...simple as that. There should be a section in your bios that is called "intergrated peripherals" and find the intergreated video setting and disable it. Now when you save the Bios and reboot your should boot to the AGP slot.
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.