1. A network video game system including a server apparatus and a plurality of client apparatuses each connected to said server apparatus via a network, said server apparatus comprising: a message collector that receives messages input in each of said plurality of client apparatuses and transmitted therefrom; and a message distributor that distributes messages in accordance with progress of a video game, including the messages received by said message collector, to each of said plurality of client apparatuses via the network; and each of said plurality of client apparatuses comprising: a message input device that inputs desired messages in accordance with the progress of the video game according to a video game player's operation; a message transmitter that transmits the messages input from said message input device to said server apparatus via said network to cause said message collector to receive the messages; a message receiver that receives messages transmitted from said message distributor; a display device that scrolls and sequentially displays all messages received by said message receiver from the message distributor of the server apparatus in a first window displayed on a video game screen, wherein each received message from a video game player is identified by displaying a name of an originating video game player adjacent to a corresponding received message from the originating video game player, that displays a current status of each video game player character that is controlled by a client apparatus in a second window displayed on the video game screen, and that does not display a current status of any video game non-player character that is controlled by the server apparatus in the second window displayed on the video game screen, wherein the first window and the second window are displayed on the video game screen simultaneously beside one another on the bottom portion of the video game screen so as not to overlap one another and so as not to visually obscure the progress of the video game, which includes video game player characters and at least one video game non-character, being displayed on the video game screen, and wherein the first window displayed on the video game screen only displays messages from game players received by the message receiver; a time counter that newly starts counting time when the time counter counts a predetermined time and also newly starts counting time when receiving a message by said message receiver; a window enlarging device that determines whether a current number of display lines for the messages in the first window is less than a preset maximum number in response to reception of a new message by said message receiver and enlarges the first window so as to increase the number of display lines by the number of lines necessary to display the received new message when it is determined that the current number of display lines for the messages in the first window is less than the present maximum number, wherein the window enlarging device can be selectably set to a first setting that displays only active messages in the first window and to a second setting that permits a display of both active messages and previously erased messages in the first window; and a window reducing device that determines whether the current number of display lines for the messages displayed in the first window is more than a preset minimum number when a predetermined condition is satisfied including a case when the time counter counts the predetermined time and reduces the first window so as to decrease the number of display lines for the messages in the first window by one message or one line when it is determined that the current number of display lines for the messages displayed in the first window is more than a preset minimum number, wherein a reduction time at which the first window is reduced may be delayed while a specific message related to the progress of the video game is displayed.