So I am upgrading the ASUS P5LP-LE (Leonite) (Details here) from a Compaq Presario SR2180NX and am having quite the dilemma. The CPU I am upgrading to is the Core 2 Duo E6600, I had this CPU in the Motherboard and had an issue where the CPU fan would spin, PSU fan would spin, any case fans or GPU fans I added would spin, but there would be no POST whatsoever. I also could not get video out of the built in VGA or my discrete GPU. I tried this with and without RAM in many different configurations to the same result, I couldn't even get a memory error beep! At this point I realized that the Motherboard needed a BIOS update in order to use my CPU, so I put the old CPU back in and had the computer in the exact configuration it was before any issues occurred to find it now acts exactly as it did with the new CPU! Mobo clearly has power, all accessories from hard drive to GPU power on, but no POST, error beeps, or video in any configuration!
TL;DR: Swapped CPU on Mobo, didn't work because BIOS was out of date, swapped old CPU back in, computer doesn't work now.
TL;DR: Swapped CPU on Mobo, didn't work because BIOS was out of date, swapped old CPU back in, computer doesn't work now.