Normally, NVR-400 will record with the best resolution without any configuration. When you play the recorded file in Windows Media Player, we will suggest you set the display screen size to full screen. Due to Windows Media Player will minify the playing video when it is not in full screen mode. So you will feel the video size is smaller than 640*480. You may move the mouse to the recorded video file and click mouse right key, then select “Properties” to check the video file information as below. You can check the Image information to make sure the record file image size.