C / C++ / MFC

#include shlwapi.h 
and to your project
import shlwapi.lib

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"We will be known forever by the tracks we leave." - Native American Proverb

LONG RegGetKeySecurity(
  HKEY hKey,                                // handle to key
  SECURITY_INFORMATION SecurityInformation, // request
  PSECURITY_DESCRIPTOR pSecurityDescriptor, // SD
  LPDWORD lpcbSecurityDescriptor            // buffer size
);
 
Parameters
hKey 
[in] Handle to an open key for which to retrieve the security descriptor. 
 
SecurityInformation 
[in] Specifies a SECURITY_INFORMATION value that indicates the <code>requested security information. </code> 
 
pSecurityDescriptor 
[out] Pointer to a buffer that <code>receives a copy of the requested security descriptor. </code> 
 
lpcbSecurityDescriptor
[in, out] Pointer to a variable that specifies the size, in bytes, of the buffer pointed to by the pSecurityDescriptor parameter. When the function returns, the variable contains the number of bytes written to the buffer. 

<br />
if(ERROR_SUCCESS != RegOpenKeyEx(...))<br />
{<br />
//Get the error code <br />
DWORD LastError = GetLastError();<br />
<br />
//Get the error code as text (example)<br />
TCHAR szBuf[80]; <br />
LPVOID lpMsgBuf;<br />
<br />
FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,<br />
        NULL, dw, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),<br />
        (LPTSTR) &lpMsgBuf, 0, NULL );<br />
<br />
sprintf(szBuf, "Error %d: %s", LastError, lpMsgBuf); <br />
MessageBox(NULL, szBuf, "Error", MB_OK); <br />
LocalFree(lpMsgBuf);<br />
}<br />