A wait window or messagebox are UI elements. You've to check the "Allow service to interact with desktop" on the Logon tab in the Service properties dialog to allow UI.

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> I have created a simple VFP application (no UI) that would run as a windows service using MS windows resource kit. I was able to installed it succesfully but the thing is when the service has already started the wait window or messagebox doesn't appear on windows desktop . I have tried to set the _screen.visible property to .T. just to make sure it would appear on windows desktop but still unsuccessful.