There are sound coming out from my power supply box .i added one casing fan and it's is fine but after 2-3 mth the power supply box start to give out sound.

There's usually only two types of sound a power supply will emmit. Fan noise and capacitor pop or cooking. Something is amiss in there.

what i hear is the fan noise . should i change it?

Are you speaking of changing the fan, or the entire power supply?

entire power supply box. Don't think it is a gd choice to change the fan.

Power supply fans can be changed, but I don't recommend it and think you are wise to go for the whole PSU. If it is the fan and it fails completely, the PSU could overheat and unfortunately, power supplies that fail have been known to take other components out with them.

Use the eXtreme PSU Calculator Lite to determine your power supply requirements. Plug in all the hardware you think you might have in 2 or 3 years (extra drives, bigger or 2nd video card, more RAM, etc.). Be sure to read and heed the notes at the bottom. I recommend you set Capacitor Aging to 30% and if you participate in distributive computing projects, I recommend setting TDP to 100%. Then look for brands listed under the "Good" column of PC Mechanic's PSU Reference List. Don't try to save a few dollars by getting a cheap supply. A good, well chosen supply will treat your digital electronics right, and provide you years of service and upgrade wiggle room.

woo thank for your guide and recommand.

Thank man i got myself a new power supply box from what digerati good brand list and Thank Dan Penny help..=)

You're welcome. Bill stated what I was going to tell you about messing around inside of power supplies, so I just let it go at that.

I'll leave this thread open for a while in case you need futher assistance.