"Case manufacturers and system builders are quite aware of this. Both of them try to incorporate system cooling into their designs. In fact, most system builders warn that changing the layout of the inside of your computer may affect the temperatures. Whether or not the impact of temperature will be something to worry about, keeping the inside of your case cool is very important. That is why, today the Tweakers Asylum will show the proper way to put a hole in the side of your case. And by proper I mean making sure to keep things safe as well."
FULL STORY @ TWEAKERSASYLUM (http://www.tweakersasylum.com/Guides/CaseMods/BlowHole/00000001.htm)