Need Help installing E6700 Core 2 Duo in Dell XPS 400?

I have a Dell XPS 400 with a Pentium D 820 Smithfield processor, 0fj030 motherboard, A03 BIOS, Northbridge i945P chipset, 4gb DDR2 RAM (PC-5300) running Windows 7 Home Premium. I installed an E6700 Core 2 Duo, as I've read can be done with this configuration, but when I boot I get nothing, nada: a yellow power button, no beeps, nothing. Any help in figuring out what I'm missing will be greatly appreciated.