Answers:
Q1: Consolidated windows is your best friend in this case, it will show all the images that are used in a UIFILE, this will help you solve the problem. 1653 is the image you need to edit to fix those corners in the chat window, I wont tell you the contact list as spoon feeding wont teach
Q2: Dash board Display Picture can't be adjusted in size due to windows live messenger restrictions
Q3: I will be explaining all these layouts in my 3rd part to my skinning guide with examples. Its a lot easier to explain this way. No ETA on it though.
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