This paper investigates the effects of power supply surges on a personal computer (PC) connected to a local area network (LAN). The surges simulated include the most common ones: surges due to lightning and capacitor switching, and fast transients due to operation of nearby end-use devices. Test results indicate that the PCs are quite immune to most of the power supply surges. Test results also give important hints towards investigating the power quality problems related to computer loads.