I have an a older HP media center PC m7250n that has been a workhorse outlasting newer laptops and desktops that have died shortly after their warranty periods ended. It's a secondary PC that I have updated with better video, a larger PS, hdd so I thought why not take the CPU to a Core2Duo on the cheap, $5. I tried another E4500 C2D CPU but still the system would not boot, nor would the CPU fan power, nor the case fan attached next to the CPU. Popped the old D820 back in and it fires right up. tried the E4500 CPUs in a Gigabyte and MSi LGA775 board and both boot. Specs show that the E4xxx and E6xxx series should work in the HP P5LP-LE board supplied by ASUS. What am I doing wrong? I have 2 of these machines and waiting to hear back before trying the second one, but I'm not optimistic about the results at this stage. I've got another custom box for the heavy PC work, but these are classics that I'd like to keep for just basic file sharing and web surfing. I'm Stumped??