Important: If you do anything mentioned on this site it is your OWN risk and I shall NOT take any responsibility for anything negative that may result.
Messing around inside of the computers hardware while it still running or while the computer is turned off but is still plugged in to a active power source can cause some costly problems! Not to mention some problems to your hands! I’ve more than once stuck my hand/fingers into the case/cpu fans and even broke a fin off of a case fan before! Obviously not working inside the computer whiles its running is a no brainer unless your lazy like me. Before working on the hardware parts of a computer you should not only turn the power off, but remove all traces of electricity.
For instance, computers can contain power even after its turned off. Its very simple to deal with this obviously. One way is by unplugging completely from the power source or by flipping the power supplys power switch off on the back of the power supply (If it has one). While that is required, the computer could still retain some amount of power.
The best thing to do is once you have removed the power source, literally try turning the computer on by pressing the power button or shorting out the power header pins on the motherboard. That will help remove any power that was retained after removing the power source. In fact, depending on how much power was retained when purging the power, the computers lights and/or fans, ect may turn on for a second or two.
Note: Just wanted to mention that the power retained in the computer may eventually fizzle out anywhere from a few seconds to maybe many seconds after you unplug it. So if you start working inside the computer as soon as you turn it off, you should definitely perform the purge procedure…
So be sure there is no power retained before working with the computers components so you dont end up frying and/or shorting any of your hardware!