Links to the original Morenatsu:
Windows 7: https://www.reddit.com/r/MorenatsuGame/comments/4pm6aw/morenatsu_download_guide/
Windows 10: https://www.reddit.com/r/MorenatsuGame/comments/i0v5in/morenatsu_windows_install...
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Best way to play the original game is through the Morenatsu Revival Port. https://www.furaffinity.net/view/25106013/
That way, you don't have to worry about installing any extra software or fiddle with your system settings.