操作注册表的API函数介绍（RegOpenKeyEx：该函数用来打开特定的注册表键）

RegOpenKeyEx：该函数用来打开特定的注册表键,注册表键值是不区分大小写的。

该远程调用接口也存在，函数名称为CeRegOpenKeyEx
LONG RegOpenKeyEx(
HKEY hKey,
LPCWSTR lpSubKey,
DWORD ulOptions,
REGSAM samDesired,
PHKEY phkResult
);
Parameters
参数
hKey
入参，标识当前被 RegCreateKeyEx 或RegOpenKeyEx打开的注册表键的句柄，或者是以下预定义的句柄
HKEY_CLASSES_ROOT
HKEY_CURRENT_USER
HKEY_LOCAL_MACHINE
HKEY_USERS

lpSubKey
入参，该参数指向一个字符串,该字符串用来保存将要打开的注册表名称。如果这个参数是空，或者是一个指向空串的指针，该函数将会打开一个由hKey所定义的键，在此种情况下，该函数不会关闭舷墙已经打开的句柄。
ulOptions
入参，保留，设置为0

samDesired
入参。标识打开注册表的权力，如果该参数的安全描述符不容许当前进程访问注册表，则该函数会返回失败。详细的安全描述见下表：

KEY_ALL_ACCESS (0xF003F)	Combines the STANDARD_RIGHTS_REQUIRED, KEY_QUERY_VALUE, KEY_SET_VALUE, KEY_CREATE_SUB_KEY, KEY_ENUMERATE_SUB_KEYS, KEY_NOTIFY, and KEY_CREATE_LINK access rights.
KEY_CREATE_LINK (0x0020)	Reserved for system use.
KEY_CREATE_SUB_KEY (0x0004)	Required to create a subkey of a registry key.
KEY_ENUMERATE_SUB_KEYS (0x0008)	Required to enumerate the subkeys of a registry key.
KEY_EXECUTE (0x20019)	Equivalent to KEY_READ.
KEY_NOTIFY (0x0010)	Required to request change notifications for a registry key or for subkeys of a registry key.
KEY_QUERY_VALUE (0x0001)	Required to query the values of a registry key.
KEY_READ (0x20019)	Combines the STANDARD_RIGHTS_READ, KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS, and KEY_NOTIFY values.
KEY_SET_VALUE (0x0002)	Required to create, delete, or set a registry value.
KEY_WOW64_32KEY (0x0200)	Indicates that an application on 64-bit Windows should operate on the 32-bit registry view. For more information, see Accessing an Alternate Registry View.
This flag must be combined using the OR operator with the other flags in this table that either query or access registry values.
KEY_WOW64_64KEY (0x0100)	Indicates that an application on 64-bit Windows should operate on the 64-bit registry view. For more information, see Accessing an Alternate Registry View.
This flag must be combined using the OR operator with the other flags in this table that either query or access registry values.
KEY_WRITE (0x20006)	Combines the STANDARD_RIGHTS_WRITE, KEY_SET_VALUE, and KEY_CREATE_SUB_KEY access rights.

phkResult
出参，指向一个变量的指针，该变量用来保存打开注册表键的句柄。如果不再使用返回的句柄，则调用RegCloseKey来关闭它。

返回值：
ERROR_SUCCESS表示该函数执行成功，非零值表示该函数执行失败。想要获得错误描述，调用FormatMessage函数，并传入FORMAT_MESSAGE_FROM_SYSTEM参数。

注意：
与RegCreateKeyEx不同，当要打开的键不存在时，RegOpenKeyEx函数不创建新键。

Requirements

Client	Requires Windows "Longhorn", Windows XP, Windows 2000 Professional, Windows NT Workstation, Windows Me, Windows 98, or Windows 95.
Server	Requires Windows Server "Longhorn", Windows Server 2003, Windows 2000 Server, or Windows NT Server.
Header	Declared in Winreg.h; include Windows.h.
Library	Link to Advapi32.lib.
DLL	Requires Advapi32.dll.
Unicode	Implemented as RegOpenKeyExW (Unicode) and RegOpenKeyExA (ANSI). Note that Unicode support on Windows Me/98/95 requires Microsoft Layer for Unicode.