I just wrote and tested the code below.  It gets the coordinates of the
Windows desktop area (screen not including taskbar) via a Windows API
call.

Jamal

require 'Win32API'

def get_desktop_area()
  function = Win32API.new('user32.dll', 'SystemParametersInfoA', ['L',
'L', 'P'], 'L')
  spi_getworkarea = 48
  structure = '    ' * 4
  function.Call(spi_getworkarea, 0, structure)
  left, top, right, bottom = structure.unpack('L4')
end

puts get_desktop_area