I don't know that everyone here knows what an EMP is, and what it actually DOES.
Someone mentioning that computer's error correction circuitry could somehow compensate for it is (not to sound rude to anyone) ignorant. Error correction circuitry won't do anything if it's completely burned out!
You have to understand what Inductance is. On an electric level, when you run current through a wire, and place a wire parallel to it, it will induce a current in the second wire. This is usually done in coils of wires, such as in a transformer, where the ratio of wires in each coil determines the voltage on the second coil.
Inducing a current can be done with magnets, after all, a magnet either attracts, or repels electrons. This is how a generator works.
An EMP is like a HUGE, amazingly POWERFUL magnet, that is only on for a split second, that INDUCES a HUGE current in any conductive materials. This current simply OVERLOADS and burns out circuitry. Integrated Circuits, like in your computers run on relatively low voltage and low current, and in an EMP, they are simply destroyed.
The case on your PC at home is not anywhere near adequate sheilding against an EMP. Of course, there would be differing magnitudes of EMPs, thus their range would vary, and destructive power also.