1. Static Electricity: Static electricity or ESD can cause numerous problems within a system. The problems usually appear during the winter months when humidity is low or in extremely dry climates where the humidity is low year-round. 2. Power-Line Noise: To run properly, a computer system requires a steady supply of clean, noisefree power. 3. Radio-Frequency Interference : Radio-frequency interference (RFI) is easily overlooked as a problem factor. The interference is caused by any source of radio transmissions near a computer system. 4. Dust and Pollutants : Dirt, smoke, dust, and other pollutants are bad for your system. The power-supply fan carries airborne particles through your system, and they collect inside.