[Kana]

From my research, supposedly the cases, and the placement of fans, and equipment like the cpu, memory, video cards etc, are taken into account with airflow and cooling. If you remove the case side panel, you may be interupting the required airflow for certain components. If your computer is overheating, opening the case is only a temporary fix. You probably have a hardware issue you should look into, or find a new cooling solution. Another reason to not have the case open, is to prevent, dust, hair, lint, smoke, etc. from readily getting into and on the internal components. Of course it does make for easier cleaning at that point, just remember to turn it off and unplug the PC before you do this.