RegQueryValueEx() always fill 0 in *lpData while reading REG_DWORD - c

Question

I have a problem with the RegQueryValueEx() function
When I use it, it fill the *lpData with 0
LONG WINAPI RegQueryValueEx(
_In_ HKEY hKey,
_In_opt_ LPCTSTR lpValueName,
_Reserved_ LPDWORD lpReserved,
_Out_opt_ LPDWORD lpType,
_Out_opt_ LPBYTE lpData,
_Inout_opt_ LPDWORD lpcbData
);
Here is the code who doesn't work
#include <windows.h>
#include <stdio.h>
int main()
{
HKEY hKey = NULL;
DWORD data = 42;
DWORD type = REG_DWORD;
DWORD size = sizeof(DWORD);
LONG result;
result = RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion", 0, KEY_READ, &hKey);
if(result == ERROR_SUCCESS)
{
result = RegQueryValueEx(hKey, "InstallDate", NULL, &type, (LPBYTE)&data, &size);
RegCloseKey(hKey);
if (result == ERROR_SUCCESS)
printf("The value is : %d\n", data);
}
return (0);
}
Output:
The value is : 0
I use Visual Studio 2012 and I'm running Win7
EDIT: Corrected line
result = RegOpenKeyEx(HKEY_LOCAL_MACHINE, "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion", 0, KEY_READ | KEY_WOW64_64KEY, &hKey);
Thanks to #David Heffernan

Answer 1

You are running a 32 bit process on 64 bit Windows. This means that you are subject to the registry redirector and so are reading out of the 32 bit view of the registry where that value really is 0. The registry redirector is mapping your key to:
HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion
Take a look in there in regedit and see that your value is 0.
You'll need to either run your code in a 64 bit process, or read from the 64 view of the registry. To do the latter, include KEY_WOW64_64KEY in the flags you pass when you open the key. More details can be found on MSDN describing how you access alternate registry keys.