Question

I need to set ActivePowerScheme by changing it in registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power\User\PowerSchemes.
So I try to do it with winapi functions RegOpenKeyEx and RegSetValueEx

wchar_t *PowerScheme=TEXT("8c5e7fda-e8bf-4a96-9a85-a6e23a8c635c");
HKEY hRootKey = HKEY_LOCAL_MACHINE;
PWCHAR sKey = TEXT("SYSTEM\\CurrentControlSet\\Control\\Power\\User\\PowerSchemes");
PWCHAR sActivePowerS = TEXT("ActivePowerScheme"); 
HKEY hKeyResult = NULL; 
//open  
if (RegOpenKeyEx(hRootKey,sKey,0,KEY_ALL_ACCESS,&hKeyResult)!=ERROR_SUCCESS) {
      //it is always failing with error 0 !
      DWORD dw = GetLastError();  
}

But RegOpenKeyEx() is always failing with error 0, that means “Operation completed successfully”. And RegSetValueEx() returns same value.

if(RegSetValueEx(hKeyResult,sActivePowerS,0,REG_SZ,
         (BYTE *)PowerScheme,wcslen(PowerScheme))!=ERROR_SUCCESS) {
                //it is always failing with error 0
                DWORD dw = GetLastError();  
            }

And of course current power scheme doesn’t change value. But according to msdn:
“If the function succeeds, the return value is ERROR_SUCCESS.
If the function fails, the return value is a nonzero error code”.

I will be grateful to any your answers.

P.S. it compiled in Windows 7 and executed with rights of admin

Answer 1

You are going about this the wrong way. You RARELY need to change stuff in the registry yourself.

Read Power Scheme Management on the MSDN site for the proper way of doing it.