ListKeys.c

#include <windows.h>

#if define UNICODE
	#define RegOpenKeyEx RegOpenKeyExW
	#define RegEnumKeyEx RegEnumKeyExW
#else
	#define RegOpenKeyEx RegOpenKeyExA
	#define RegEnumKeyEx RegEnumKeyExA
#endif

#define MAX_KEY_LENGTH 255

HKEY Open(HKEY root,LPTSTR path, REGSAM permission)
{
	HKEY hKey;
	LONG lResult = RegOpenKeyEx(
		root, //HKEY_LOCAL_MACHINE,  HKEY_USERS,  HKEY_CURRENT_CONFIG,  HKEY_CLASSES_ROOT,  HKEY_CURRENT_USER
		path, // the path of the key
		0,    // must be 0
		permission, //KEY_WRITE, KEY_READ, KEY_ALL_ACCESS, KEY_QUERY_VALUE, KEY_ENUMERATE_SUB_KEYS
		&hKey // OUT : The result [pass by refrence]
		);

	if (lResult == ERROR_SUCCESS)
		return hKey;
	return INVALID_HANDLE_VALUE;
}

void Close(HKEY hKey)
{
	RegCloseKey(hKey);
}

void ListKeys(HKEY hKey)
{
	DWORD index = 0, SubKNameLen = MAX_KEY_LENGTH;
	CHAR SubKName[MAX_KEY_LENGTH];

	while (ERROR_SUCCESS == RegEnumKeyEx(hKey, //Opned key to a specific path
		index,  // incremental counter
		SubKName, // OUT : return key name
		&SubKNameLen, // IN max key lenght & OUT : return key length
		NULL, // Reserved
		NULL, // OUT : class name
		NULL, // IN : max class length & OUT : class length
		NULL  //Last Write Time
		))
	{
		printf("%s\n", SubKName);
		SubKNameLen = MAX_KEY_LENGTH;
		index++;
	}
}

int main()
{
	HKEY hKey = Open(HKEY_CURRENT_USER, "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Explorer", KEY_ALL_ACCESS);
	if (hKey != INVALID_HANDLE_VALUE)
	{
		//do your job
		ListKeys(hKey);
	}
	Close(hKey);
	return 0;
}