One of the first classes in any elementary level PC hardware course tells the students to be careful when handling computer hardware, ie:
do not touch the electronic circuits on interface cards or memory chips with your fingers; in other words handle these items by their edges but also be careful not to touch the connectors by which these items are attached to the computer's motherboard
do not drop or even jar hard disks especially when placing a hard disk on a hard surface such as a desk
power down and disconnect the PC from the wall power outlet during thunderstorms to avoid power spikes
wear an anti-static wrist strap when working on the internal components of a PC to avoid electostatic discharge (ESD)
It has been my experience that most people fail to strictly adhere to these precautions as, over time, they see, for example, that they can insert a RAM chip into a computer's motherboard without wearing an anti-static wrist strap and without any adverse consequences. It is true that most of these precautions can be disregarded and, most of the time, no harm may result. It is also true however that computer electronics are sensitive to static electricity and power spikes and just because you have carried out an operation once without problems doesn't mean that will always be the case.
One simple example from my own personal experience; one day as a thunderstorm was approaching, I went to shut down my PC and disconnect the power cord from the wall socket. I shut down the PC OK but, in my hurry to disconnect the power cord, I pulled the cord out of the wall socket without turning off the wall socket switch first. As I did so, I saw a spark jump between the cord and the socket and sure enough the PC's motherboard was damaged and had to be replaced.
References:
Mueller, Scott: "Upgrading and Repairing PCs", Que
Andrews, Jean: "A+ Guide to Managing and Maintaining Your PC", Course Technology
