recently the PSU fan is so loud, i dont know why, maybe i need to add some oil? if i hit the back of the PSU(the fan), it actually quiet(back to normal) for 1-3 seconds, then back to loud again. any idea? thanks! 3.2GHZ Intel Pentium EE 840 1GB Dual-channel DDR2-533 RAM Asus P5ND2-SLI Deluxe mobo 2 EVGA E-Geforce 7800GTX Creative Soundblaster X-Fi 550W PSU

It's probably caked with dust and/or the oil on the bearings is dried up. You can clean it off by using a compressed-gas duster. Never open up your power supply to clean it though and make sure it is not plugged in.

but what if its not dust, its the oil is dried up, how do i fix it? 3.2GHZ Intel Pentium EE 840 1GB Dual-channel DDR2-533 RAM Asus P5ND2-SLI Deluxe mobo 2 EVGA E-Geforce 7800GTX Creative Soundblaster X-Fi 550W PSU

If your fan has been making noises for a while, there may have been times when it has spun too slowly or has stopped, causing your power supply to overheat - that may have already damaged your power supply. Before you do anything, take a look in your bios/cmos Setup pages and find the current voltage readings for your motherboard and power supply - the ones for +3.3, +5, and +12 volts should be within 10% of their nominal values - the core voltage for the cpu should be within 5% of it's nominal value. If any of those are out of whack, you need to replace your power supply, as soon as you can If those voltages are okay..... "...how do i fix it?" If you don't want this problem to repeat itself, you replace the fan. It is usually a standard 80mm size, inexpensive, and easy to find at any place that has a reasonable selection of computer fans. If you connect a new fan inside the PS case, usually it only needs to have 2 wires. However, in most cases you can use a case fan of the same size, and feed it's 3 wire connector and wires out of the PS case and connect it to the motherboard so it's rpm can be monitored. Just make sure it has ball bearings, preferably on both sides, and it's wattage or current rating is the same as the original one, or more. A good fan has ball bearings on both sides and never needs to be oiled. Some fans have a ball bearing on one side, on the side inside the PS, and a sleeve bearing on the other, which you can oil by opening up the label on the fan in the center at the back of the power supply, IF you can get at that area. El- cheapo power supply fans often have two sleeve bearings. Oiling a sleeve bearing is a waste of time - if the bearings are making noises they are already badly damaged, and it will only help for a short while. In any case, if the fan has two sleeve bearings, you would have to open up the PS case to oil the inner one, and you would have to remove the fan blade and put it back on without damaging it - you might as well just replace it. "Never open up your power supply to clean it though and make sure it is not plugged in." Some people think working on a power supply is dangerous, even when it is unplugged - it isn't in reality. The power supply has large capacity capacitors that are used to help stabilize the voltages supplied to the motherboard - the better the power supply, the longer these capacitors can hold enough charge to give you a zap after the computer is unplugged - but they discharge all on their own in just a few minutes when connected to the motherboard and the PS is unplugged. If you have an led on the mboard that is on even when the computer is shut down but it is plugged in, when you unplug the computer, when that led goes out the capacitors have discharged. If you don't have an led like that, just wait 5 minutes after unplugging the power supply with the motherboard still connected and the capacitors will be discharged. In any case, to just change a fan, you don't need to go near the capacitors or their bare connections (which are mostly on the bottom of the power supply board) in any case. If opening up the power supply case and replacing the fan is beyond your expertise, eventually the PS fan will stop turning, the power supply will overheat and eventually die, and you will need to get another power supply.

o thanks a lot man, i will try. hopefully it will help. i have never messed with the bios, so i dont think the setting has changed. the interesting thing is when i hit/knock it, it back to normal(quiet), then loud again. 3.2GHZ Intel Pentium EE 840 1GB Dual-channel DDR2-533 RAM Asus P5ND2-SLI Deluxe mobo 2 EVGA E-Geforce 7800GTX Creative Soundblaster X-Fi 550W PSU