Service + DLL + Display Questions

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Sorry for my bad english...
I develop on WinXP and MFC. My main program called mainDialog include a dll with a view. It works. The second program install the mainDialog as a service program (Local System Account), it works too. When i start my computer and i log on the mainDialog, the mainDialog is visible (Data exchange between service and Desktop is checked). My Question... What is the best way? I would like to start the mainDialog as service (invisible) and in the user account as program (visible), when the user like it. The mainDialog must be running as one instance.
I hope you understand me, thx for your answers.
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