If you are even close to correct in stating that the "zap" was from an INCH away, then this MUST have been a static electric shock. That distance takes many many thousands of volts, and NO actual electrical supply to your system can provide that. Actually, the fact that you DID get a brief shock means it is VERY likely that the computer case WAS Grounded so that there is a place for the charge to go to. But that is not guaranteed. It is possible if you are "charged up" statically to discharge that to a completely isolated computer case which has no charge. "No charge" is still much less than a "charged up" you.
Even static electric discharges can damaged solid state devices when a current is forced THROUGH the device. Although the...