3.9.2.1 Windows NT/2000/XP/Vista?

• From Chris McMahon. To make CapsLock a Control key (leaving your original control keys as they were), use this registry file:

  REGEDIT4
  
  [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
  "Scancode Map"=hex:00,00,00,00,00,00,00,00,02,00,00,00,1d,00,3a,00,00,00,00,00
  

  To swap CapsLock and the left Control key, use:

  REGEDIT4
  
  [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
  "Scancode Map"=hex:00,00,00,00,00,00,00,00,03,00,00,00,1d,00,3a,00,3a,00,1d,00,00,00,00,00
  

  Save these as files with a .reg extension, and double-click on them in Explorer, or “run” them from a command prompt to have them update your registry (you may need to reboot).

• Shane Holder gives some background on how "Scancode Map" is used by the system:

  It's a binary value that lets you map keystrokes in the low-level keyboard
  drivers in NT.  As a result you don't have to worry about applications
  bypassing mappings that you've done at a higher level (i.e., it just works).
  
  Here's the format of the value:
  
  	DWORD:	0x00000000	header
  	DWORD:	0x00000000	header
  	DWORD:	length (in DWORDs) of remaining data, including terminating DWORD
  	DWORD:	mapping 1
  	...
  	DWORD:	mapping n
  	DWORD:	0x00000000	terminating null DWORD
  
  Each mapping DWORD  has two parts: the input scancode, and an output
  scancode.  To map scancode 0x1d (left control) to scancode 0x3a (caps
  lock), you want a value of 0x003a001d.  Note that this does not swap the
  keys.  Using just this mapping value, both the left control and the caps
  lock key will behave as caps-lock.  To swap, you also need to map 0x3a to
  0x1d, using 0x001d003a.
  
  This registry value is system wide, and can't be made user-specific.  It
  also only takes affect on reboot.
  

• Ulfar Erlingsson has provided a registry file that sets the CapsLock key to be a Control key and the Windows key to be an Alt key:

  REGEDIT4
  
  [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
  "Scancode Map"=hex:00,00,00,00,00,00,00,00,03,00,00,00,1d,00,3a,00,38,00,5b,e0,00,00,00,00