Hello, I need some help trying to upgrade my computer. I have a Dell Dimension 4600i and I purchased the p4 3.0 ghz socket 478 processor with hyper-threading. I put it in the stock dell mobo and powered it back up and get nothing. Get green light on the board all the fans spin on psu, video card, etc., etc., but my screen stays dark. No boot screen, no beeps, nothing. Concerned I put the 2.8 back in it and it does the same thing, nothing. Im a little lost here please help. Thanks in advance.