[lmikle]

Открываем MSDN и читаем:

hKey [in]
A handle to an open registry key. The key must have been opened with the KEY_SET_VALUE access right. For more information, see Registry Key Security and Access Rights.
This handle is returned by the RegCreateKeyEx, RegCreateKeyTransacted, RegOpenKeyEx, or RegOpenKeyTransacted function. It can also be one of the following predefined keys:

Теперь смотрим функцию RegCreateKeyEx:

LONG WINAPI RegCreateKeyEx(
__in HKEY hKey,
__in LPCTSTR lpSubKey,
__reserved DWORD Reserved,
__in_opt LPTSTR lpClass,
__in DWORD dwOptions,
__in REGSAM samDesired,
__in_opt LPSECURITY_ATTRIBUTES lpSecurityAttributes,
__out PHKEY phkResult,
__out_opt LPDWORD lpdwDisposition
);

Еще пояснения нужны?

ЗЫ. И не забудь закрыть ключ после записи.