litestep is not a skinning program therefore it won't change your xp luna theme.
if you're using an OTS theme (I asume you are) you must be sure that you haven't set the desktop area in your personal.rc or any of the included files. Look for jDeskWorkArea "X1,Y1,X2,Y2" or
SetDesktopArea
SDALeft X1
SDARight X2
SDATop Y1
SDABottom Y2