Dude you got a dell!
It sounds like an irq issue, try inserting something into pci 1. Try to boot, if it boots leave the card in there.. Then try a card in pci 2.. If it boots sweet leave it there. Try a card in the third slot if it doesnt work, try switching the card from pci2 to pci 3 and leave pci 2 empty. Go into the bios and see if you can set irqs?