I cannot remove the fan to replace the cpu...

Sounds like the processor is getting an overheating code and shutting the system down or the processor is cooked and can no longer function. If you are trying to get an intel cooling fan off an intel chip, there should be four posts holding the fan in place, these posts turn 90 degrees and then when all four are turned , pull the fan off the mount. If yours does not have the four post mount, then it may have clips on either side of the heatsink, these should just be pried away from the mount and the heatsink will be free. If the heatsink is stuck to the processor, you will need a flat plastic pry tool to wedge under the lip of the proc and heatsink to separate them.