Your tablet monitor/lcd-screen have to support the resolution the fullscreen game starts in. In fullscreen-mode your monitor change its resolution while in windowed-mode resolution stays the same, only window size changes. Almost every one supports 640x480 but 960x720 is a tricky one. You can try to "force alternate letterbox resolution" to match a resolution you monitor supports but there is no workaround if your monitor capabilities are limited.Well, some drivers let you customize your monitor resolutions list so you can add one (but not higher than maximum) but I strongly advise you not to do so since you can damage your monitor this way.