I've probably already messed up this question. I thought I had it tracked down, but in double checking based on your questions, it appears that I was wrong about the source, which is once again unknown. I can now only feel the current in the case when the CPU power supply is on. The outlet is properly grounded and I now felt the shock with the monitor completly disconnected. There has to be some sort of a short some where, although it is not messing up operation of the computer. No smoke, no sparks. Everthing seems to work fine,except for the tell tale tingle when you touch the case. I picked the cpu up second hand, so I don't know what has been done to it. Any ideas?