Unplugged computer sparked upon touching a cold heating pipe
If it was just a tiny spark like touching a door knob after walking on carpet, then it's normal &amp; harmless. If it was actually a flash, then something's either grounded to the plumbing &amp; defective or a live wire's in contact with the plumbing.

Most likely, the circuit that the circuit breaker killed &amp; is the problem circuit &amp; must be fixed immediately as it could harm or kill someone.