Friend's PC working in my home, not in his

This is an earthing/wiring issue and is really something an electrician needs to look into. What you have described could be dangerous and unsafe to fix.

You have not mentioned where you are (matters from an electrical code pov. You might want to confirm this. Relatedly, do you have a multimeter ?

If you are getting shocks that means electricity has an alternative path to ground. One thing you can try us getting the thickest cable you can find and a big metal pole/rod. Bang the pole nearly all the way into the ground, and run the cable from the pole to a metal part of the computer case. This will ground the case and may be useful and safer then it is now. Really though, a sparky should be looking into this and possibly correcting this at the mains board.