-The case has the primary function of housing, ventilating, powering, block transmission of EMF.
-Housing, this is pretty major for obvious reasons. You don't want to spill your Budweiser on the motherboard now do you?
-Ventilating, we really want to keep a eye on this one. Most of the time a good ATX case can keep a moderate amount of components cool with no problem. The best thing to do is make sure the case is properly cool and having a fan on the CPU along with one case fan other than the power supply fan is a good idea. I use this same setup on my system and it runs cool all day.
-Power Supply, this is in most case's already installed. Again we really want to go with the ATX case and stay away from the ole AT. The power supply is overlooked much but is extremely important. When a power supply starts to act up you may actually think its another device giving you trouble. This can be some very expensive trial and error in your future. Buy good stuff from brand names!
-EMF, well as you guessed the government came in on this one. The case has to keep the internal components that generate EMF to a low. This is (Electromagnetic Frequencies) and can interfere with your TV, radio, cordless phones, and so on.
