I\'m launching my Windows application this way after the installation completes:
!define MUI_FINISHPAGE_RUN_FUNCTION \"LaunchApplication\" ... Function LaunchA
Use Exec '"$WINDIR\explorer.exe" "$TEMP\MyUnElevatedProcess.exe"'
Exec '"$WINDIR\explorer.exe" "$TEMP\MyUnElevatedProcess.exe"'
Taken from http://mdb-blog.blogspot.com/2013/01/nsis-lunch-program-as-user-from-uac.html