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An easy selection is piece of cake in Xara.
Open the bitmap, give it a flat transparancy of some 50%, create a new layer and draw your outline. Then fill it so as to see whether it is perfect, copy to clipboard and delete layer, activate bitmap layer and undo transparancy, paste, put the shape perfectly on the bitmap and combine shapes> subtract (or intersect, I don't remember as I do it automatically.) Then you have your bitmap shape without background.
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You don't have to copy to clipboard and delete layer... just select both objects and hit combine shapes - intersect (for the keyboard enthusiast... hold down ALT and hit R-C-I ... I always just remember R-adio C-ontrol and then A-dd S-ubtract I-ntersect

Later,
Robert