Electrical Shock from Faulty/Improperly Grounded Computer

Have you ever experienced electrical shock from your computer? Yesterday I got electrical shock when I touch any metal part of my PC case. Then I straight away testing my power extension socket and yes it was the problem of the socket, it failed to ground the electricity to earth. Checking the socket was my first step to find out the problem was because of this experience. Two of my friends bought their PC at the same time last year, I helped them to install windows after came back from Low Yat. And we got electrical shock from both computer cases, we even can felt the shock from the back of the connected LCD monitor. It wasn't static shock, we can felt continuous electricity flowing through the case! When we touched any metal part of the computer, we will get high electrical shock(really painful...) from it. Even the painted area of the case got moderate electrical shock. At first, we suspected there was power leakage from the hardware, before my friends decided to go back to Low Yat, I figured out it was the faulty grounding of the power extension socket. The extension socket that connected from wall socket to another 4-plugs power socket got problem and was not grounded. After we switched it with another power socket, both PC back to normal, no more electrical shock from all parts of the PC, problem solved.