Step Three: Ventilation
Many PSUs have poor intake slits for ventilation. This can cause a lot of noise as the fan sucks air through all of the small slits in the case.
To help alleviate this noise simply locate a clear area on the housing of the PSU (other than on the side where you plan on placing a window) and cut long slits across the face. I used a nibbler to cut mine, but if you use a Dremel or similar tool cut them about 1/4 inch wide so that plenty of air can pass through them.
Step Four: The Window
Adding a window to your PSU is just like adding one to your case side. Simply cut a hole in the side of the PSU housing (the one facing your window) leaving about ½ inch to glue in the window.
Here is the window masked off just before I cut it out. For this part I used a Dremel.
The window itself can be made from nearly any clear plastic, I used overhead transparency for mine due to space constraints, however using the front of a cd jewel case, or even a thin piece of plexi would work fine. If you plan on painting your PSU do it before install the window so that you don't have to mask off the plexi. To install the window simply glue it in with your favorite bonding agent (I used silica sealant).
Here is the window after its been glued in:
After these few simple mods your PSU should be a bit quieter with the new fan and added ventilation and a bit better looking thanks to that window you added. Here are some final pics from this project.
Hope this mini-guide helped you out in customizing your own power supply!