Dear Dirk,
It depends on who wrote the program and what code they used to do
that. It varies even amongst Microsoft teams. Like the "MS Office"
team will preset "My Documents" or "Documents" (Vista). as a default.
Some other app may select "desktop". The function called can be a
standard "Shell" browse class (object actually) or the common dialog
classes in Windows, or another 3rd party "browser" code. I guess I'm
saying that you can't customise until you know which module is being
used. Certainly there are registry settings for messing with the
common dialog browse dialog. But only for "My Places" and other
standard things.
http://support.microsoft.com/kb/826214
Good luck,
CreateWindow