First, let's use the right terminology to avoid confusion. You don't turn on a CPU. The CPU is device the size a postage stamp that mounted on the motherboard inside, the computer case. You turn on the "computer".
it sounds like you have no earth . i dont know if you have them over there i am from uk and at 240v with an earth
By "Earth" he means there appears to be no good path to electrical "ground", or Earth as it is called in Europe. And yes, physics works the same way all around the world, and electricity is controlled by the Laws of Physics so electronics needs to be properly grounded no matter where it is. Even in airplanes and in outer-space where the engineers use a "common" "floating ground" to tie all the equipment to - so they remain at the same potential.
This "open ground" you seem to have can be dangerous. Remember, anything that plugs into the wall can kill!
You need to do a couple things immediately
. Go to your local home improvement store and buy an AC Outlet/Ground Fault Indicator Tester
. There is a model for every common voltage and plug type so don't worry if yours is different than the one shown. Then check your wall outlets. If not correct, have an electrician fix them before someone is electrocuted.
Note, every home should have one of these outlet checkers, and every outlet in the house or apartment should be checked.
Make sure all the computer peripherals are plugged into the same wall outlet. No two wall outlets, even if only 6 feet apart, have the exact same electrical characteristics, and may have a slightly different resistance to ground. This difference between the two outlets causes a "difference in potential" (voltage) and can be felt in the manner you describe. And if great enough, can be dangerous to equipment, people and pets. If the wall outlets are fine, and all the power cords have been checked for damage or replaced, if you still have this issue, then there's a fault in one of your components causing a difference of potential between them. If using a surge and spike protector, try a different one, or better get, get an UPS with automatic voltage regulation (AVR). Surge and spike protectors are little more than fancy and expensive extension cords that do nothing for sags, dropouts, or extended surges. Therefore, I recommend all computers be on a UPS with AVR.
Good luck and be safe.