Hello, Please look at the image below: (Click for animation) Notice that the "Red" section appearing instantly before the Main GUI... Code: #include-once ; -- Created with ISN Form Studio 2 for ISN AutoIt Studio -- ; #include <GUIConstantsEx.au3> #include <WindowsConstants.au3> #Include <GuiButton.au3> Global $test_gui = GUICreate("test",300,300,-1,-1,-1,-1) GUISetBkColor(0xFFFFFF,$test_gui) GUISetState(@SW_SHOW, $test_gui) Global $test_child_gui = GUICreate("test child", 150, 150, 0, 0, $WS_POPUP, $WS_EX_MDICHILD, $test_gui) GUISetBkColor(0xFF0000, $test_child_gui) GUISetState(@SW_SHOW, $test_child_gui) While 1 Switch GUIGetMsg() Case $GUI_EVENT_CLOSE Exit EndSwitch WEnd How can I prevent it? Thanks in Advance

Original answer from this post by binhnx, you should have a look at it if you need more information (Also to know the cons of using the following solution) . This post is made to make life easier for people who have been suffering from this problem Here is your answer: #include-once ; -- Created with ISN Form Studio 2 for ISN AutoIt Studio -- ; #include <GUIConstantsEx.au3> #include <WindowsConstants.au3> #Include <GuiButton.au3> Global $test_gui = GUICreate("test",300,300,-1,-1,-1,-1) GUISetBkColor(0xFFFFFF,$test_gui) GUISetState() ; This is the faulty statement: Global $test_child_gui = GUICreate("test child", 150, 150, 0, 0, $WS_POPUP, $WS_EX_MDICHILD, $test_gui) Global $test_child_gui = GUICreate("test child", 150, 150, 0, 0, BitOr($WS_CHILD, $WS_VISIBLE, $WS_CLIPCHILDREN, $WS_CLIPSIBLINGS), -1, $test_gui) ; You should change the faulty statement to the above correct statement to avoid the "Aero Window Apperence Delay" effect.... GUISetBkColor(0xFF0000, $test_child_gui) GUISetState() While 1 Switch GUIGetMsg() Case $GUI_EVENT_CLOSE Exit EndSwitch WEnd Before: (click images to animate them) After: TD