Abstract: A method of unlocking usable memory space of a portable memory device, such as a flash drive, includes connecting the portable memory device to a network access device, such as a computer. The network access device executes a control program and accesses a website through the network access device by execution of the control program. A specific task is executed at the website, which sends an unlocking code upon completion of the task. The usable memory space of the portable memory device is unlocked in response to receiving the unlocking code at the network access device.