Hi
I managed to have some time and look to the DX7 SDK there is a sample called fswindow that does just what you want.
The problem is that the sample creates a surface (fancy name for a linear area of display memory), I tried to instead enumerate the surfaces and see if I can get FS2002 surface but it didn't enumerate. The main problem seems to be "how to access another process surface"
I don't agree completely with Pete regarding FS2004 if the supported DX version will be DX9 and if the DX7 methods are compatible I think that the applications will work. I hope since I like DF734 a lot. :)
Best
José