[1]Why is it important to have (earth) ground connected to one's
computer or any appliance, equipment, etc. that has three-pronged AC
plugs?

Because then the equipment attached to that ground will have a stable ground
potential, that is, 0 volts will mean the same thing to every piece of
equipment attached to the ground.  Also, the ground provides a path for
current from a static shock or internal short circuit to flow.

[2]Is it the case that earth ground plays an integral role in the
engineering and function of any surge suppressor, UPS, or line
conditioner?

Yes, in that consistent voltage measurements from one piece of equipment to
another may become impossible if there is no single ground reference.
Again, these devices may also rely on the ground to "shed" excess voltage.

[3]If someone is moving into a home whose outlets are not grounded (to
do so would be very costly as the concrete foundation is not raised),
how might they protect their sensitive electronic equipment like
computers and peripherals?

They really should seek a licensed electrician.  I'm sure that it could be
done themselves, but I certainly wouldn't want to risk making a mistake.  It
should not be all that costly for an electrician to run the ground wires
through the walls and out to a grounded metal rod.

[4]In the case of number [3], is using GFI outlets their only option?

No, GFI outlets don't provide the kind of protection that sensitive
electronic equipment requires.  They were designed to protect people from
electric shock, but people aren't as sensitive to electric shock as
electronic parts.  For example, the static shock that you feel when you see
a spark represents about 30,000 volts of electricity (at a very low
current).  That's something like 6 times what it takes to potentially fry an
electronic component in a computer.  A GFI outlet is designed to respond to
a short circuit by tripping very quickly.  But "quickly" to a GFI circuit is
in human terms...it should trip fast enough that a hair dryer dropped in a
bathtub won't injure you or me, but it won't respond to the kind of voltage
spikes and surges that could damage a computer.

[5]Can one assume that, if an appliance, computer, etc. has a
three-pronged outlet that its circuitry is designed to exploit the
advantages of earth ground in the event of over-current or over-voltage?

No, but you might be able to assume that the appliance has established a
reference voltage of 0 volts that is comperable to the 0 volt reference of
other electric appliances in your house.  Also, if there is an electrical
problem within the appliance, you might expect that the ground will provide
a path for the current to follow, instead of shocking you.  But you may not
be able to completely depend on this.  The best way to tell if the ground is
used in the appliance (or computer) is to test for continuity between the
ground prong of the cord going into the wall outlet and any exposed metal
parts of the appliance.  Any multimeter can do this.  If you test the
equipment, remember that paint and other coatings on the metal are
non-conductive.  Test bare metal.

Electricity is pretty serious business.  Grounding needs to be done
correctly or you can be injured or killed.  That's not to say that houses
with ungrounded outlets are deathtraps, but if the outlets are to be
grounded, they must be done so correctly so that you know that you are
working with properly grounded equipment.  You need to know what you are
working with to make smart decisions.

Drew Dunn

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