Monitor has some voltage !!

Recenlty, i bought a wireless adapter which i wanted to place it into the motherboard, so simply shut down the PC and tried opening the side cover the case but it had some shock waves in it (electricity), so i unpluged the power cable and still was the same, so i just did wear gloves and fixed the adapter, and closed the case, and it still sometimes gives some voltages when you try to touch it, special if ur not expecting it.. My friend told me that he had the same problem, and it was due to the monitor power cable, and he says that he fixed it by cutting the original plug of the monitor power cable and fixing another one, but i didnt give it any attention since i dont touch my pc that often, but recently i touched my monitor screen while cleaning it and noticed that it also have some voltages in, and you feel like there is some vibration of some sort, then thought that my friend might been right, but before replacing the plug, i wanted to ask here if anyone had similier issues and how it was fixed...

Thanks in advance