agree'd with 13thmonkey, most likely incompatibility of the cpu to the motherboard. Most likely u have a 125watt cpu in a board that only supports 95watt cpus. As said most likely will need a new board to work with the cpu or cpu for ur current board. Some boards that only take 95watt downclock the cpu alot to even boot with 125watts but im guessing the board u have doesnt lol