Vista Aero design philosophy or a bug?
As far as I know, from Windows 2000 onwards, calling MessageBox API with MB_OK, MB_OKCANCEL shows the message dialog with [X] (close, cross)button enabled, while, using MB_YESNO shows it with [X] button disabled. I thought Design Philosophy behind this would be, X button is more or less to dismiss the dialog (which is same as canceling it). While, NO would not exactly mean canceling the dialog and hence X button is disabled.
Here is the interesting (or buggy?) part: On Vista, same MessageBox API with MB_YESNO shows dialog with [X] button disabled in non-aero or classic look, while, turning on the AERO effect, we see this [X] button enabled. Nothing happens when we click on it.
Is this a bug or Aero design philosophy? only Microsoft can answer.