Take a fresh formated and reinstalled windows seven.
It has HTML5 in Internet Explorer 9.
Flash isn't supposed to be there, and the plugin needs to be downloaded and installed to be effective.
Moreover one of the things that many people (including Scirra's members) expect that HTML5 will get rid of flash. (take over it in the mid to long term)
Making a core/official plugin relying on flash defeats this purpose.