I have a customer with a high end Dell tower. It is running 8.1. For the last year that they have owned this tower it will randomly lock up so that all applications are locked, but the mouse still moves. Other times it completely locks up and the only way to turn off is to shut power (power button will not shutdown computer by holding for 10 secs), other times the power button will work. Other times not all icons or tiles show up. Could this be software, or is this more likely a hardware issue? What would be your line of attack on this?