Q: I removed the casing since its not that well ventilated.
A: You sure would! Though, I highly doubt an ill health will come about by removing the side panel. The amount of radiation emitted from a computer is small. The largest emitter of radiation is actually your monitor. If you have an older CRT monitor (big TV looking things), you should worry more about replacing that with an LCD. LCD's have a lower rate of emissions, though they still emit some radiation. Overall, your computer and monitor is not likely to cause any health problems. The amount of naturally occurring radiation is much higher then a computer system. Annually we are all exposed to about 200 mrem of radiation from the air in the form of radon gas. While using a computer frequently is exposing you at about 1 mrem annually. In fact, taking a round-trip cross continental flight will expose you to five times the amount of radiation emitted from a typical computer.