The Power Reset function resets the virtual machine. It is similar to powering off and on the virtual machine. Resetting the virtual machine loses the state of your guest operating system. It is usually better to use the normal reboot procedure of the guest operating system, or to shut down the guest operating system before resetting the virtual machine.
Warning: if you are using a nonpersistent disk, all information written to the disk since the last virtual machine power on will be lost.