Please, always try to search the forums before making a new thread to avoid duplicated threads. As for this issue, several threads already exist which explain all in detail. 
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As stated in that
linked post provided by Spunky, it only works on the
offline/full installer (which is more than 7MB big).
With the exception that a "Thank you"-webpage will always be opened at the end of the setup.
It will not work on the online/web installer (which is less than 500KB big).
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Also see another thread:
Messenger Plus! 5.02.0.712 silent install parameters
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