https://bugs.winehq.org/show_bug.cgi?id=41700
--- Comment #3 from Dmitry Timoshkov dmitry@baikal.ru --- (In reply to Alex Henrie from comment #0)
The "Install Now" and "Customize installation" buttons do not appear on either the regular Python 3.5 installer or the Python 3.5 web installer, not even if you hover the mouse over the buttons or press the tab key repeatedly. However, the installation continues if you click where the button should be, and the tab key appears to move focus onto and off of the buttons even though there is no visual feedback.
Note that you must set the Windows version to Windows Vista or later in winecfg or the installer will only show you an error message.
Actually Python 3.5 installer should work under XP too, and under XP the aforementioned buttons are also missing. That's a bug in the class library (can't recall its name off the top of my head, but it's open source) the installer is using.