You are assuming you did not damage the socket removing old CPU and installing new CPU. Basic process of elimination is system that was working and did not work after changing CPU, but when original CPU is re-installed system works it's bad CPU. Your system is not now working with original CPU, meaning the CPU you bought may not be the problem. It might be that somehow there was damage to CPU socket while changing CPUs. Not saying this is for sure, but it is a possible cause of problems like this that we've seen here on forum before. Hopefully it's just the new CPU is bad, but socket damage/bent pins could possibly be the cause of your problem.