The Super User question [How to make ^ and ` non-dead-keys on Windows 7 with German keyboard layout](http://superuser.com/questions/280005/how-to-make-and-non-dead-keys-on-windows-7-with-german-keyboard-layout) is about the reverse situation. In an answer, [Tobias Plutat suggests](http://superuser.com/a/280032/151741) to use **The Microsoft Keyboard Layout Creator**, which allows you to

> assign or un-assign dead key behavior

The tool [can be downloaded from microsoft.com](https://msdn.microsoft.com/goglobal/bb964665.aspx). According to its installation requirements, Windows 7 is supported (on the download page you get redirected to, it no longer lists Windows 7, but that documentation seems to be for the older version 1.0, not the current 1.4).

As I’m not using Windows, I couldn’t try it, but at least on GNU/Linux the behaviour you desire is the default one if <kbd>^</kbd> is set as **dead-key** (except for <kbd>^</kbd>+<kbd>u</kbd>, which creates `û` instead of `ŭ`), so I assume it should be the same for Windows. At least the `â` is listed on Microsoft’s [Common Dead-Key Combinations](https://msdn.microsoft.com/en-us/library/cc195156.aspx).