:PostMessage(hWndPrev,WM_UPDATA_CAIGOUFROMOLD,0,0)2003下运行正常在XP下报错,该如何处理

::PostMessage(hWndPrev,WM_UPDATA_CAIGOUFROMOLD,0,0)2003下运行正常在XP下报错
::PostMessage(hWndPrev,WM_UPDATA_CAIGOUFROMOLD,0,0)2003下运行正常在XP下报错

------解决方案--------------------
WM_UPDATA_CAIGOUFROMOLD值是不是大于65535?