It is useful to disable Windows UNC patch checking in order to be able to open a command prompt anywhere.
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Command Processor] "DisableUNCCheck"=dword:00000000
Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Command Processor] "DisableUNCCheck"=dword:00000001