Loud Power Supply FAN!

[potatorage]

Well if the wd-40 did not work there is another cheap fix.
Use mineral oil. The oil is non conductive, i have had a whole entire setup minus the hdd and dvd drives in a fish tank of it. But for your case that would be a little extreme, no noise at least.
Fill a Tupperware container with about 3in of mineral oil then sink the end with the fan into the container. let it sit for five minutes then pull it out and let it dry or at least stop dripping and put back in.
I have done this with fans that were noise and slow but after this they worked just like new.
you will have to do this once a year at least to keep them working.

That's way too much oil. Just put a drop on the bearing and that should be enough

 

[Benm]

I would recommend replacing the fan. Adding a lubricant like WD40 or mineral oil can temporarely relieve the problem (and both are non conductive), but the problem is likely to be caused by either wear or contamination.

Your concern for capacitors retaining charge and giving you a proper shock is quite real - most power supplies have buffer caps that charge up to the mains voltage top (300V on a 230V system) and those can deliver a dangerous jolt.

One way of discharging them before doing any work is to actually pull the cord from mains with the system still running (bios screen is fine). Doing so is likely to discharge the caps, since the system cannot cease using power before the caps are depleted.

To ensure a safe situation for work: measure. You can easily identify those caps, usually fairly large ones with a 350/400V rating printed on them. Just measure with a multimeter set for DC voltage prior to doing any work. If you want to, yo can connect a 10k resistor across the multimeter leads to facilitate discharge, and doublecheck they are actually empty.

Getting a zap from such buffer caps is very unlikely to cause permanent injury (as in heart failure and such), but it can cause nasty local electrical burns that take forever to heal.