No Flash in IE7 on Windows Vista? Here is the fix
So the problem behind this is Vista's User Account Control (UAC) which, on installation of the Flash plugin, can't modify certain registry keys (even though you are an admin), but doesn't tell you about the failure (which is not a good thing).
The solution? Go to "C:\Windows\System32\Macromed\Flash" and right-click on FlashUtil9b.exe, the select "Run as administrator".
Afterwards, you should be able to view Flash content in the browser.