As mentioned in Locking down that Desktop,
you can replace the shell by editing:
HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon\
and replacing Explorer.exe with YourOwnShel...
If the prospect of moving all
those shares to your new server has you down, here is a simple
method that will only take a few minutes. Navigate to the
following registry key:
HKEY_LOCAL_MA...