you special person, you, you somehow managed to screw up the skin. i don't see how you could have even done that when ALL your should be editing is the Startup.xml file. DO NOT edit anything else, it is completely unneccessary.
you should simply try changing the <posx> and <posy> tags for the image. they tell XBMC where the top left corner of the image starts, so basically they control where it gets displayed on the screen. i'm assuming you have already properly calibrated the UI to your TV? if not, please do that before continuing.