Jeg aner ikke hvor du sætter det i registry, men du kan jo lave en genvej til explorer og give den nogle parameter.
Her er syntax for explorer.exe udtrykket fra microsoft.
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Syntax
EXPLORER.EXE [/n][/e][,/root,<object>][[,/select],<sub object>]
Switches
/n: Opens a new window in single-paned (My Computer) view for each item
selected, even if the new window duplicates a window that is
already open.
/e: Uses Windows Explorer view. Windows Explorer view is most similar
to File Manager in Windows version 3.x. Note that the default view
is Open view.
/root,<object>: Specifies the root level of the specified view. The
default is to use the normal namespace root (the
desktop). Whatever is specified is the root for the
display.
/select,<sub object>: Specifies the folder to receive the initial
focus. If "/select" is used, the parent folder
is opened and the specified object is selected.
Examples
To open a Windows Explorer view to explore only objects on \\<server name>, use the following syntax:
explorer /e,/root,\\<server name>
To view the C:\WINDOWS folder and select CALC.EXE, use the following syntax:
explorer /select,c:\windows\calc.exe