Motherboard replacement XPS One 2710

Hello

My XPS 2710 suddenly gave me blank screen and after calling Dell i was informed that it needed a new motherboard.

I bought the motherboard and installed it but when I turned it on it gave me continuous four beeps. I turned it off and on again but this time when it is on, it shuts off immediately.

did I do any thing wrong with the processor? what it is the solution in this case?

Thanks