In the top-level-form of the application you can check if there is already a windows with the same caption. In the init-event I use this code for that purpose:
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Local wHandle, cCaption
Declare integer SetForegroundWindow in Win32Api integer
Declare integer FindWindow in Win32Api string, string
With this
cCaption = .caption
.caption = "Where is "+upper(cCaption)+"?"
wHandle = FindWindow(0,cCaption)
If wHandle > 0
SetForeGroundWindow(wHandle)
Quit
Endif
.caption = cCaption
wHandle = FindWindow(0,.caption)
SetForeGroundWindow(wHandle)
Endwith
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It's not foolproof! The code looks for a window with the same caption, so if there is a window that complies the assumption is that it is the application whereas it might be something completely different like an explorer-window showing a folder with the same name.
It works fine for me (VFP6 and VFP8 on Win95 .. WinXP).