I'm probably just being dense but when I run both of these scripts (compiled) I don't detect any difference in the user experience. (am running Windows 8.1 64b) SystemModal #include <GUIConstantsEx.au3>
#include <MsgBoxConstants.au3>
$hGUI = GUICreate("Test", 500, 500)
GUISetState()
MsgBox($MB_SYSTEMMODAL, "SystemModal", "Press me to continue")
While 1
Switch GUIGetMsg()
Case $GUI_EVENT_CLOSE
Exit
EndSwitch
WEnd TopMost #include <GUIConstantsEx.au3>
#include <MsgBoxConstants.au3>
$hGUI = GUICreate("Test", 500, 500)
GUISetState()
MsgBox($MB_TOPMOST, "TopMost", "Press me to continue")
While 1
Switch GUIGetMsg()
Case $GUI_EVENT_CLOSE
Exit
EndSwitch
WEnd