Permanetly change the close.png icon

[Egg Bramhill]

I dislike the default close icon that Xara uses to close a pop-up layer if Close Automatically is unchecked.

I can always replace it in the index_htm_files folder, however each time I republish it will revert back to the Xara default.

How would I change it permanetly by overwriting it in Xaras root file. Can anyone point me in the right direction please?