My cpu fan will not shut off it is so loud should i replace the fan or is there a way to repair this problem

A really loud fan can be one of two things - neither is very good to have for very long. Most newer motherboards support multi-speed fan operation based on CPU temperature. This keeps fan noise at a minimum because the fan only has to run fast (and loud) if the CPU exceeds a specific threshold temperature. The loud noise could also be from a fan that is starting to fail and is binding, thus running slower than normal. Either of these conditions is indicative of a problem that kills PCs - heat. Open the case and carefully examine the heat sink fins and the fan on the CPU. If they are caked with dust (especially the fins), then the CPU will likely overheat and shut down. Get some canned air designed for cleaning electronic components and blow the dust from the fins and the fan. Restart your system a see if the fan runs slower and quieter now, Machines that are in dusty environments, around smokers, or placed on the floor are especially prone to dirt buildup. Periodic cleaning with the canned air is the way to keep your PC happy and healthy.

When the CPU overheats then it will shut down (i.e. thermaloverload) and won't boot up again until it has cooled down. If this is theproblem is not fixed then the CPU will eventually fail.
A faulty fan causes the problem or the fan and heat sink assembly are cloggedwith dust.
Check the CPU fan to see if it spins freely, if not replace the fan.
If the fan and heat sink is clogged with dust the remove the dust and make surethe vents are clear and dust free. Use a can of compressed air to do this.

Check your BIOS Settings

CPU Configuration
CPU Internal Thermal Control [Auto]
Hyper Threading Function [Enabled]
Intel(R) SpeedStep(tm) Tech [Auto]

Power>Hardware Monitor
CPU Q-Fan Control [Enable]
CPU Fan Ratio [Auto]
CPU Target Temperature [60degC] (lowest setting available)

or you can replace it with Cooler Master XDream

When the CPU in the computer or laptopoverheats then it will shut down (i.e. thermal overload) and won't boot upagain until it has cooled down. If this is the problem is not fixed then theCPU will eventually fail.
A faulty fan causes this problem or the fan and heat sink assembly are cloggedwith dust.
Check the CPU fan to see if it spins freely, if not replace the fan. If the fan and heat sink is clogged withdust the remove the dust and make sure the vents are clear and dust free. Use acan of compressed air to do this.

It could be the cooling fan to the power supply but it sounds like that went completely out and blew the Zenor Diode or something in the power supply. You can test the voltages coming off the power supply to make sure. If that is what happened you are better off simply replacing it. You can get them at Best Buy for about $40 and it is a simple 4 screws to remove in order to trade them out. Make sure you have the correct connectors for the motherboard. If the Power supply is good then you lost the CPU fan. If the CPU fan went out and the computer will no longer start up you may have cooked the CPU. Again, this is something you can replace fairly easily. The fan should run about $12 to $20 depending on what model you get and what type of CPU it has to mount to. The hard part will be the CPU itself. If it has overheated to the point of burning a connection inside the CPU will have to be replaced and while it should not be soldered on the board the heat sink will be very difficult to get off and when you put the new heat sink on to the old CPU or a new one you will need heat sink compound. Runs about $1 a tube. If the CPU just overheated and shut down the PC should restart once it has cooled if nothing else till the CPU heats back up. Usually takes a couple of minutes but not long. This is actually good news if this is what is happening as it means the CPU is most likely operational and that is the expensive part to repair in an over heat situation. The problem does sound like a blown power supply though. If you have to replace the heat sink and CPU fan once you get the old stuff off and as much of the old heat sink compound off as possible make sure you apply new compound to the CPU. You do this by applying a small amount to the center of the CPU and pressing the heat sink into place, this should spread the compound evenly and thinly over the CPU area and form a bond between the heat sink and the CPU to transfer heat between them. The fan normally attaches to the heat sink and locks down on the CPU. Connect the Fan power wires into one of the power supply sockets and everything should come on when you power on the computer. While you have the case open you should take the opportunity to use canned air to blow the dust out of the case and air circulation holes. Heat and Dust are not your friends in computers. Good luck with your repair.

May be your CPU Fan has been faulty.So you can replaced it.

You might have a cooling problem due to a fan malfunction. It is not clear whether it's the power supply fan or the CPU fan; in the latter case you might also have a thermal coupling problem. The symptoms you describe certainly seem to point to such.

My advice would be to replace the fan (or the whole power supply; you might also want to purchase a "Silent Power" unit for quieter computing). If it's the CPU fan and you are comfortable with, or know anyone comfortable with a bit of PC servicing, you might want to also unmount the heat sink from the CPU and replace the thermal paste between CPU and heatsink. Clean the heat dissipator (the black metal grille over the heatsink) with hot water and a bit of soap and dry thoroughly, or wipe it energically with a dust brush, before mounting the new fan on it.

This sounds like either a power supply issue or a CPU fan issue to me. You say you hear a fan spinning loudly. Try and determine which fan it is. Take the left side panel off your case and start your game. When the fan gets loud identify which one it is. It's possible that the heatsink on your CPU is clogged up (pet dander, dust, smoke, etc.) and needs to be blown out. Get a can of compressed air and try blowing out the inside of your PC. It's possible your CPU/video card/power supply is just getting too hot.

It is possible that the CPU has overheated. You  should replace the buzzing fan and reseat the CPU. If that doesn't work my guess is that the CPU will have to be replaced. 

check your cables. it may be in the way of the fan's fins. also clean your fan for dust.