It is amazing how much play this discussion has had. To answer your 
specific question, I looked inside my case. Assuming that the hard 
drives, optical drives and floppy drives are internally insulated, it 
appears that the motherboard and other components are insulated from the 
case. Therefor, grounding oneself to the case carries no danger to the 
computer innards. And assuming that the power supply is also internally 
insulated, I do not see how discharging oneself to the case would result 
in a discharge to the house circuit through a connected grounded power 
cord whether the power supply is on or off. The static discharge is to 
the air from the case. If one were to carry this to an extreme, the case 
could have a separate grounding wire attached going to a separate 
grounding rod.

There are many instances of similar static discharges to non grounded 
items during one's lifetime. The most frequent one I've experienced is 
touching metal desks and file cabinets that are sitting on wood floors. 
Second on the list would be touching vehicles.

If a static discharge is to a component (the reason for protecting the 
computer from oneself), the component is likely history before the 
discharge even gets to the air or to some grounding provision. On the 
other hand, if the desire is to protect oneself from the computer, at 
least turn the power supply off at the power supply or simply disconnect 
the power supply from the power source. And as an added precaution, do 
not put fingers where they do not need to be.

Tom

Robert Citkowitz wrote:
> What-if question:
>
> If you connect yourself to the uplugged computer via wrist strap, couldn't you be zapping the computer/chips with whatever static charge you had built up (eg, the surprising, sparking amount you get during the dry winter after walking on a carpet) on the way to the computer?
>
> Rob 
>
>
>   

               The NOSPIN Group Promotions is now offering
                 our special coffee mugs and mouse pads
              with the PCBUILD logo...  at a great price!!!
             http://freepctech.com/goodies/promotions.shtml