I know I can rearrange the applications in my taskbar in Windows 7, but there doesn't seem to be any way to rearrange the previews for each window. For example, I have Firefox open and the Downloads window open, and for some strange reason the Downloads window is now the left-most window, while the Firefox browser window is number 2. I'd like to rearrange those two so the main browser window is first, but I can't drag or drop them. Is there a power tool to enable this?
This is a duplicate of: Arrange windows within the same application in the taskbar of Windows 7
The answer listed there is to install "7 Taskbar Tweaker" from here: 7Taskbar Tweaker
You can reorder the thumbnails by checking the box "Drag to reorder" under the "Thumbnails" section in 7 Taskbar Tweaker. It works now like it should!
If you don't want to use that approach (which requires the program to be running in the background all the time), then just launch Taskbar Tweaker when you need it and you can click the "Taskbar Inspector" button and drag around instances of your app inside of the app group and they will move in realtime.
I can't offer a generic solution but in the particular case you describe you can press Ctrl + J three times when the main Firefox window has focus.
1st time - bring Downloads window to foreground
2nd time - close Downloads window
3rd time - open Downloads window
End result is that the main Firefox window preview is displayed to the left of the Downloads preview.