关于C++删除注册表项遇到问题，含泪求助。

大家好，本人正尝试用C++编程来删除注册表的某个键及其所有子键，相关程序在MSDN上找到了，却遇到如下问题很奇怪：
RegDelnode(HKEY_LOCAL_MACHINE,
TEXT("SOFTWARE\\Test123"));就失败


RegDelnode(HKEY_CURRENT_USER,
TEXT("SOFTWARE\\Test123"));就成功

进一步试验也得出，凡是HKEY_LOCAL_MACHINE里的键值就不能删，而HKEY_CURRENT_USER里的键值就可以删除，我百思不得其解，明明删除键值的函数里的两个参数的第一个就可以在HKEY_CURRENT_USER、HKEY_LOCAL_MACHINE等等里面选择的，怎么会选择性失明？我具体写的时候是用MFC写的，代码基本没变，附CSDN上的代码如下，大家帮忙分析一下：

#include <windows.h>
#include <stdio.h>
#include <strsafe.h>
using namespace std;
//*************************************************************
//
// RegDelnodeRecurse()
//
// Purpose: Deletes a registry key and all it's subkeys / values.
//
// Parameters: hKeyRoot - Root key
// lpSubKey - SubKey to delete
//
// Return: TRUE if successful.
// FALSE if an error occurs.
//
//*************************************************************

BOOL RegDelnodeRecurse (HKEY hKeyRoot, LPTSTR lpSubKey)
{
LPTSTR lpEnd;
LONG lResult;
DWORD dwSize;
TCHAR szName[MAX_PATH];
HKEY hKey;
FILETIME ftWrite;

// First, see if we can delete the key without having
// to recurse.

lResult = RegDeleteKey(hKeyRoot, lpSubKey);

if (lResult == ERROR_SUCCESS)
return TRUE;

lResult = RegOpenKeyEx (hKeyRoot, lpSubKey, 0, KEY_READ, &hKey);

if (lResult != ERROR_SUCCESS)
{
if (lResult == ERROR_FILE_NOT_FOUND) {
printf("Key not found.\n");
return TRUE;
}
else {
printf("Error opening key.\n");
return FALSE;
}
}

// Check for an ending slash and add one if it is missing.

lpEnd = lpSubKey + lstrlen(lpSubKey);

if (*(lpEnd - 1) != TEXT('\\'))
{
*lpEnd = TEXT('\\');
lpEnd++;
*lpEnd = TEXT('\0');
}

// Enumerate the keys

dwSize = MAX_PATH;
lResult = RegEnumKeyEx(hKey, 0, szName, &dwSize, NULL,
NULL, NULL, &ftWrite);

if (lResult == ERROR_SUCCESS)
{
do {

StringCchCopy (lpEnd, MAX_PATH*2, szName);

if (!RegDelnodeRecurse(hKeyRoot, lpSubKey)) {
break;
}

dwSize = MAX_PATH;

lResult = RegEnumKeyEx(hKey, 0, szName, &dwSize, NULL,
NULL, NULL, &ftWrite);

} while (lResult == ERROR_SUCCESS);
}

lpEnd--;
*lpEnd = TEXT('\0');

RegCloseKey (hKey);

// Try again to delete the key.

lResult = RegDeleteKey(hKeyRoot, lpSubKey);

if (lResult == ERROR_SUCCESS)
return TRUE;

return FALSE;
}

//*************************************************************
//
// RegDelnode()
//
// Purpose: Deletes a registry key and all it's subkeys / values.
//
// Parameters: hKeyRoot - Root key
// lpSubKey - SubKey to delete
//
// Return: TRUE if successful.
// FALSE if an error occurs.
//
//*************************************************************

BOOL RegDelnode (HKEY hKeyRoot, LPTSTR lpSubKey)
{
TCHAR szDelKey[2 * MAX_PATH];

StringCchCopy (szDelKey, MAX_PATH*2, lpSubKey);
return RegDelnodeRecurse(hKeyRoot, szDelKey);

}

void main()
{
BOOL bSuccess;

bSuccess = RegDelnode(HKEY_CURRENT_USER,
TEXT("Software\\TestDir"));

if(bSuccess)
printf("Success!\n");
else printf("Failure.\n");
}