That CPU has a 125w TDP. The motherboard can not take CPU's with a TDP greater than 95w. So, that CPU is not going to work in that motherboard. You'll have to put in the original CPU or get another one.
As obsama said your new CPU is not compatible with the old motherboard. You either have to use the old CPU or buy a new one. I'm guessing this is an OEM big box computer. If that is the case and if you decide to get another CPU check the computer manufactures website and find the CPU compatibility list.