Whenever I see a post like this, I wonder why the poster didn't just return the non-working part to the vendor they bought it from. This might be my US bias, but very few vendors put it on the customer to prove a certain level of testing and diagnostic activities; if the customer says it didn't work, the customer gets their money back. If you're not sure if it's the motherboard or the CPU or... return it all, and try again. No?