Strange computer noise failure, and computer application problems

Computer recently inexplicably noise, are buzzing hum, very large, do not know where is issued, generally as long as the indoor air-conditioning will be open noise. Have not before, now have, sometimes boot to select the operating system and then cut off the power cord, and then plug in the power cord can be resolved. Sometimes plug the power cord can also be resolved. Sometimes it is not possible to pass these methods. And sometimes in the noise, the BIOS also has a line in English, the effect is the CPU frequency from 2.93Ghz down frequency to 1.8Ghz. But there is noise and can be normal boot. There is no need to press F1 to enter the system when there is noise.

Also, gigabyte motherboards (H61, Awardbios) How to brush slic to activate Win7 (note, no OEM);

Suspicion is the power supply fan vibration generated by the body resonance, you put the chassis stand up and see the sound becomes small, the basic conclusion is that resonance, or small, is the sound of the fan

The feeling is the power, the boot when close to the ear to listen to the specific where,

Of course, sometimes the CPU fan will also be wired more messy words, may scrape to the fan leaf.

Inside the chassis can be "moving" parts only mechanical hard drives and fans, hard drive will not make such a big sound, it must be the fan thing, to save trouble directly all replace the fan and then the hair dryer clean and clean.