Have you applied power to it yet? If not, my advice is not to. Dell has a nasty habit of making their own proprietary motherboards and power supplies. Dell mobo plus standard power supply equals sparks and destruction.
Anyone here familiar with that particular Dell model and know if it can live with a standard power supply? siliconali42000, do you have a manual that shows the power pinouts for the motherboard, so you can compare then to the ATX standard?
If I had to upgrade a Dell, first I would try to get a power supply from Dell, then I would drill extra holes in the case if I knew that the PS was compatible. I like Dell machines, I like Dell service. My wife and daughter have a Dell. But I would never play with the hardware.
EDIT: I hope that I am wrong and everything goes well for you.