Why this code cannot change caption of "Start" button?

[Steve S.L. Wong]

I try to change the caption of Start Button of Windows (mine is Windows ME):

import win32gui
import win32con
import win32api
import array

hwnd = win32gui.FindWindowEx(win32gui.FindWindow('Shell_TrayWnd',None),0,
                               "Button",None)

win32api.SendMessage(hwnd,win32con.WM_SETTEXT,0,
                     array.array('c','TEST' + '\0').buffer_info()[0])

print 'LPARAM is: %d' %  array.array('c','TEST' + '\0').buffer_info()[0]


Any body knows why the above code does not work?