안녕하세요.
아래코드는 이곳에 발취하여 사용하는 Code인데요 (볼륨 조절용)
Xp에서는 정상적으로 MasterVolum을 제어하는데 ,  OS가  Window7(vista)에서 서브 볼륨만 제어가 됩니다.
Windows7에서 프로그램으로 Master볼륨을 제어해야되는 어떻게 해야하는지요?

그리고 SendMessage를 이용하여 한번 해봤는데 이것도 안되네요  뭐가 문제일까요?
void __fastcall TForm1::Button1Click(TObject *Sender){
     HWND hWnd = GetDesktopWindow();
     if(hWnd)
     {
          SendMessage(hWnd, WM_KEYDOWN, VK_VOLUME_UP,0);
     }
}

여러분의 많은 조언 부탁드립니다.

void SetSpeakerVolume(float fVolPercent)
{
    HMIXER hmx;
    mixerOpen(&hmx, 0, 0, 0, 0);

    MIXERLINE mxl;
    mxl.cbStruct = sizeof(mxl);
    mxl.dwComponentType = MIXERLINE_COMPONENTTYPE_DST_SPEAKERS;
    mixerGetLineInfo((HMIXEROBJ)hmx, &mxl, MIXER_GETLINEINFOF_COMPONENTTYPE);

    DWORD cConnections = mxl.cConnections;
    for(DWORD j=0; j<cConnections; j++){
        mxl.dwSource = j;
        mixerGetLineInfo((HMIXEROBJ)hmx, &mxl, MIXER_GETLINEINFOF_DESTINATION);
        if (MIXERLINE_COMPONENTTYPE_DST_SPEAKERS == mxl.dwComponentType)
            break;
        }

    LPMIXERCONTROL pmxctrl = (LPMIXERCONTROL)malloc(sizeof (MIXERCONTROL));
    MIXERLINECONTROLS mxlctrl = {sizeof mxlctrl, mxl.dwLineID,  MIXERCONTROL_CONTROLTYPE_VOLUME, 1, sizeof (MIXERCONTROL), pmxctrl};
    if(!mixerGetLineControls((HMIXEROBJ) hmx, &mxlctrl, MIXER_GETLINECONTROLSF_ONEBYTYPE))
    {
          DWORD cChannels = mxl.cChannels;
        if (MIXERCONTROL_CONTROLF_UNIFORM & pmxctrl->fdwControl)
            cChannels = 1;

        LPMIXERCONTROLDETAILS_UNSIGNED pUnsigned = (LPMIXERCONTROLDETAILS_UNSIGNED)malloc(cChannels * sizeof (MIXERCONTROLDETAILS_UNSIGNED));

        MIXERCONTROLDETAILS mxcd = {sizeof(mxcd), pmxctrl->dwControlID, cChannels, (HWND)0, sizeof (MIXERCONTROLDETAILS_UNSIGNED), (LPVOID) pUnsigned};

        mixerGetControlDetails((HMIXEROBJ)hmx, &mxcd,MIXER_SETCONTROLDETAILSF_VALUE);

        float fvoldist, fsetvol;
        fvoldist = pmxctrl->Bounds.dwMaximum - pmxctrl->Bounds.dwMinimum;
        fsetvol = fvoldist * (fVolPercent / 100.0);
        DWORD newvol;
        newvol = pmxctrl->Bounds.dwMinimum + (DWORD)fsetvol;
        pUnsigned[0].dwValue = pUnsigned[cChannels - 1].dwValue = newvol;

        mixerSetControlDetails((HMIXEROBJ)hmx, &mxcd,MIXER_SETCONTROLDETAILSF_VALUE);

        free(pmxctrl);
        free(pUnsigned);
        }
        else
        free(pmxctrl);

    mixerClose(hmx);
}