Because the operation and control of most critical infrastructures are highly dependent on electronics, it is important to understand the feasibility and effectiveness of devices that may be used to intentionally interfere with electronic system operation. This research project investigated (1) the feasibility of building a high power electromagnetic interference source from a common consumer item and (2) the effects of this source on the operation of personal computers. We were successful in fabricating a “shop-expedient” high power microwave (HPM) source by modifying a common microwave oven. Project results confirm that, with straightforward modifications, a common microwave oven can be turned into an effective EMI source that is capable of disrupting personal computer operation at close ranges.