Sometimes the application buttons on the Windows 7 taskbar change position by themselves. For example, if I have two windows of the same application opened, the first opened window should be the first button on the taskbar (to the left of the other) and the second opened window should be the second button on the taskbar (to the right of the other), but they switch places sometimes. I don't like this. How can I fix / configure this not to get rearranged?

I am not using Aero, and the buttons of the same application are not grouped under a single button.

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