If you wish to open Regedit.exe at a specific key:

1. Create a RegKey.bat file that contains:

@echo off
setlocal
if \{%1\}
\{\} goto prompt
set key=%1
if \{^%key:~0,1%\}
\{^"\} goto open
set key="%key%"
:open
if /i \{^%key:~0,5%\}
\{^"HKLM\} set key=%key:"HKLM="HKEY_LOCAL_MACHINE%&goto get
if /i \{^%key:~0,5%\}
\{^"HKCU\} set key=%key:"HKCU="HKEY_CURRENT_USER%&goto get
if /i \{^%key:~0,5%\}
\{^"HKCR\} set key=%key:"HKCR="HKEY_CLASSES_ROOT%&goto get
if /i \{^%key:~0,4%\}
\{^"HKU\} set key=%key:"HKU="HKEY_USERS%&goto get
if /i \{^%key:~0,5%\}
\{^"HKCC\} set key=%key:"HKCC="HKEY_CURRENT_CONFIG%
:get
if /i \{^%key:~0,30%\}
\{^"HKEY_LOCAL_MACHINE\System\CCS\} set key=%key:"HKEY_LOCAL_MACHINE\SYSTEM\CCS="HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet%
set regedt=HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Regedit
reg.exe ADD %regedt% /v LastKey /d %key% /f>nul 2>&1
if NOT %ERRORLEVEL% EQU 0 @echo %regedt% NOT found.
endlocal
start regedit.exe
goto :EOF
:prompt
set /p key=Enter the key to open. 
if \{^%key:~0,1%\}==\{^"\} goto open
set key="%key%"
goto open

2. There are 3 ways to use RegKey.bat:

      A.1. Create a shortcut to the RegKey.bat file.
      A.2. Set the icon of this shortcut to Regedit.exe.
      A.3. Set it to run in a normal window.
      A.4. Double-click the icon and enter the key or "".

      B.1. Start / Run / RegKey <The Key> / OK or
      B.2. Start / Run / RegKey "" / OK.

      C.1. Open a CMD prompt.
      C.2. Type RegKey <The Key> and press Enter or
      C.3. Type RegKey "" and press Enter.

NOTE: Reg.exe is from the Windows 2000 Support Tools or the Reg.exe that is built into Windows XP and later.

NOTE If you implemented tip 2358, How do I prevent Regedit from using the last state, you must undo the permissions change.

NOTE: You could also implement tip 6200, How do I prevent Regedit from remembering the last key, without altering registry permissions, and use it instead of RegKey "".

NOTE: I have implemented the following abbreviations that you can use:

Abbreviation	Key
HKLM	HKEY_LOCAL_MACHINE
HKLM\SYSTEM\CCS	HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet
HKCU	HKEY_CURRENT_USER
HKCR	HKEY_CLASSES_ROOT
HKCC	HKEY_CURRENT_CONFIG