Do
NOT leave the computer plugged in!!!! Those that say to leave it plugged in are untrained, unsafe, unprofessionals. Period. There is NO "middle ground".
1. There are deadly voltages inside a power supply,
2. You must not assume the power supply does not have a manufacturing defect or has not been damaged by physical or electrical abuse,
3. You cannot assume, without professional testing, that your house is properly grounded,
4. You cannot assume, without professional testing, that that wall outlet is properly grounded, or wired, or undamaged,
5. Do not trust your life to a $.25, mass-produced power cord,
6. Do not trust that $.25 power cord to provide a proper ground,
7. Do not trust your life to a $.25, mass-produced master power switch (if your PSU is so equipped).
8. The ATX Form Factor Standard REQUIRES +5Vsb ("standby") voltages be distributed across multiple points on the motherboard when the power supply is plugged in - even when the computer is powered off!!! This voltage is necessary for the front panel power switch and several "Wake on" features available on all computers made since ATX was adapted 15 years ago. This voltage can only be removed by unplugging the computer from the wall, or, IF equipped, by the [optional] $.25 master power switch on the back of the power supply.
What should the occasional user do to change memory or a drive
It is important to note that you don't have to be "grounded" (or Earthed, as they say in some parts of the world) to safely work on electronics (unless you are working on "live" electronics, but that is never necessary with computers). But you
MUST be at the "same potential" as the computer. If you are at the same potential, there can be no current "flow" and therefore no static discharges (arcs and sparks).
So what should the occasional user do? Great question! The most important thing is probably just being aware. Be aware that just wiggling in your clothes can generate damaging static levels, not to mention squirming in your chair or as you noted, working on the carpet. The problem with static and high-density ESD (electro-static discharge) sensitive devices like memory chips and other IC devices is that a static discharge can be well below the threshold of human awareness yet more than enough to totally destroy the device. That is, static electricity can arc (discharge) from your finger tips and destroy a CPU or memory module or another motherboard component without you even being aware a discharge occurred.
To change RAM,
unplug the computer from the wall, and put the computer on a hard flat surface. Open the side panel and touch bare metal of the case to discharge any static in your body - this puts you at the same potential as the case. In effect, you and the case are now at the same "floating ground" potential. A wrist strap is a good idea but cheap ones have cheap clamps, and can be affected by sweat, dirt, etc. on your wrist. So I recommend to still touch bare metal frequently, or even constantly, if possible, and definitely before reaching in. I try to keep a finger touching all the time.
Other precautions for RAM include never touching the electrical contacts of the modules, and make sure you have them properly oriented and aligned before inserting. For other devices, don't touch the bare circuits like exposed circuit boards or connector contacts.
