A disclosed computer system having a virtual computer management mechanism realizing a virtual computer includes a user virtual computer that communicates with a device via a virtual computer for a device driver under a control of the virtual computer management mechanism, an input receiving unit that receives a signal of an input operation from the device, a reset level determination unit that determines a reset level based on the received signal of the input operation, a reset target specifying unit that specifies a virtual computer to be a target of a reset process based on the determined reset level, and a reset signal transmission unit that transmits a reset signal to perform the reset process on the specified virtual computer.