dude.. your problem may have different root causes..
in general what you want to do is the following:
1. make sure everything is seated properly and test
2. make sure your memory sticks are compatible to *********** board, installed in the right slot(s) and test again
3. make sure your power supply is working properly and power plugs are properly seated (use it in another systme or teste it with ps tester and test again
do you hear a series of beeps?, is there any video going to the screen? any errors??
uninstalled any new hardware you had and leave the system with the minimum to work. motherboard, video card (use onboard), sound card (use onboard) network card (use only onboard if any), mouse, keyboard. and test.
things to try before blaming the motherboard or the processor is to read check for bios updates or confim you're using compatible hardware for your mb, here's the link for the manual, drivers, updates from the manufactorer for your motherboard..
good luck.. post more details of your problem if you need follow up