Cannot boot Gparted (or any other USB/CD) on a Dell Vostro 200

Cannot boot Gparted (or any other USB/CD) on a Dell Vostro 200

Very strange problem. Trying to get Leopard installed on a Dell Vostro 200 Minitower but can't get past Step Zero. Didn't boot of a formatted USB key, so I burned a Gparted ISO and tweaked the BIOS appropriately but get