I've dabbled in PC hardware tweaks, but nothing like that, so I asked my pal Chuck Eglinton about this and here's his take:

Generally, once you open the box and look inside you'll know right away how easy or difficult replacing the CPU fan or power supply will be.

On some computers, I've found replacing the power supply to be very easy, and on some, you may have to remove the main board or other brackets, first. You'll just have to pop off the case and take a look.

Often, you simply need to unscrew four Phillips screws that attach the power supply to the back of the case, then lift the power supply out or lift it off of some retaining hooks that are die stamped. Of course, you'll need to have a clear path to where the cables connect on the main board so you can disconnect and reconnect the cables. You can't attach the cables incorrectly because they're keyed.

If you can get to your CPU fan, its usually held in place by a spring hook retaining mechanism. If you replace it, don't forget to use thermal grease as recommended upon installation.

Fortunately, power supplies and CPU fans are inexpensive on eBay and all over the Internet.

If all else fails, you can buy some very long cables on eBay and place the noisy CPU in another room.

Hope that helps you out!