We stayed at a rental property and the stove used to give shocks at seemingly random times of the day. My dad, an EE, finally figured it to be the water heater was not grounded right and when it kicked on caused the problem.
I could be remembering that wrong, and it's not necessarilly the water heater, but you could go to the fuse box and turn off a bunch of items (other rooms) and try and narrow down which item / circuit may be making the situation worse. For example, turn off all other rooms but the office and see if you still get shocked by the pc.
/While my dad is an EE, I am not, so, the above is really just another bump for an update.