uses
        System;  // please be sure to add System unit in your uses clause

procedure OpenOrCreateMyKey;
var
  res, resdisp, del_res: DWORD; // res is the result of the create function,
                                // if the function success the return is
ERROR_SUCCESS
  phkey                : HKEY;
begin

  // two methods, RegCreateKeyEx is safer than OpenKeyEx because if the
specified subkey doesn't exists
  // it will create it for You. These are available simpler methods, too,
called RegOpenKey, RegCreateKey (no Ex)
  // first method
  res := RegOpenKeyEx(HKEY_LOCAL_MACHINE, // handle of open key or predefined
constant
                     'SOFTWARE\BLEBLE',  // name of subkey to open
                     0,                         // reserved, must be zero
                     NIL,               // security access mask
                     phkey              // handle of open key
                     );

  // second method, better
  res := RegCreateKeyEx(HKEY_LOCAL_MACHINE, // predefined constant or handle to
key opened before
                       'SOFTWARE\BLEBLE',  // name of subkey to create, can be
full path, except ROOT Key name
                       0,
                       NIL,
                       REG_OPTION_NON_VOLATILE, // for Windows NT
                       KEY_ALL_ACCESS,          // for Windows NT, You can
leave it and use always this constant
                       NIL,                        // security attributes, requires special
handling, leave it NIL
                       phkey,              // here will be returned handle to newly
opened/created key
                       @resdisp);
{
resdisp - >

Points to a variable that receives one of the following disposition values:

Value   Meaning
REG_CREATED_NEW_KEY     The key did not exist and was created.
REG_OPENED_EXISTING_KEY The key existed and was simply opened without being
created.

  RegCloseKey(phkey);                      // always close no more needed key handle
end;

// Deleting key
// first open something like before, or give predefined constant value
procedure DeleteMyKey;
begin

  del_res := RegDeleteKey(HKEY_LOCAL_MACHINE, 'SOFTWARE\BLEBLE');

end;

//Windows 95: The RegDeleteKey function deletes a key and all its descendents.
//Windows NT: The RegDeleteKey function deletes the specified key. This
function cannot delete a key that has subkeys.

// Documentaion taken from Win32 SDK Help File

{
hKey

Identifies a currently open key or any of the following predefined reserved
handle values:

HKEY_CLASSES_ROOT
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS
The key specified by the lpSubKey parameter must be a subkey of the key
identified by hKey.

lpSubKey

Points to a null-terminated string specifying the name of the key to delete.
This parameter cannot be NULL, and the specified key must not have subkeys.