RegSetValueEx() not changing the key value - c++

Question

In my application, when I first set the key-value using RegSetValueEx() it works, but when I try to change the value using the same function it doesn't work, the value remains same. What am I doing wrong ?
Here is the code :
SetSZValue( "MyAppData", "versionInfo", "1.0.0" );
HKEY CreateKey( string regkey )
{
HKEY hKey ;
DWORD disValue ;
char msg[512] ;
string _key = "HKEY_LOCAL_MACHINE\\" ;
_key += regkey ;
LONG retValue = RegCreateKeyEx( HKEY_LOCAL_MACHINE, regkey.c_str(), 0, 0, REG_OPTION_NON_VOLATILE, KEY_ALL_ACCESS, 0, &hKey, &disValue ) ;
if (retValue != ERROR_SUCCESS)
{
FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM, 0, GetLastError(), 0, &msg[0], 512, 0 ) ;
MessageBox( 0, &msg[0], "CreateKey", MB_OK | MB_ICONEXCLAMATION );
}
return hKey ;
}
void SetSZValue( string regkey, string keyName, string keyValue )
{
HKEY hKey;
DWORD disValue;
char msg[512];
hKey = CreateKey(regkey);
if (hKey)
{
LONG retValue = RegSetValueEx( hKey, keyName.c_str(), 0, REG_SZ, ( const BYTE* )( keyValue.c_str() ), keyValue.size()+1 );
if ( retValue != ERROR_SUCCESS )
{
FormatMessage( FORMAT_MESSAGE_FROM_SYSTEM, 0, GetLastError(), 0, &msg[0], 512, 0 );
MessageBox( 0, &msg[0], "SetSZValue", MB_OK | MB_ICONEXCLAMATION );
}
RegCloseKey ( hKey );
}
}

Answer 1

RegSetValueEx accepts the name of the value inside the key to change; not the name of the key. Supply the value name instead; the key name comes from the HKEY itself.

Answer 2

Is your app a 32-bit process running on a 64-bit Windows version? If so, does your app have a UAC manifest with a "requestedExecutionLevel" value in it? If not, your key may be getting virtualized to another section of the Registry and you are simply not looking in the right place. Registry Virtualization is a feature of WOW64 so legacy 32-bit and 64-bit processes do not step over each other in the Registry. You should install SysInternals Process Monitor, it will show you which keys and values your app is actually accessing.