#include <ddraw.h>
#pragma comment(lib, "Strmiids.lib")


    static void LogOutVideoMemory()
    {
        LPDIRECTDRAW2 lpdd;
        HRESULT ddrval;

        CoInitialize(NULL);

        ddrval = CoCreateInstance(CLSID_DirectDraw,
            NULL, CLSCTX_ALL, IID_IDirectDraw2, (void**)&lpdd);


        if(!FAILED(ddrval))
        {
            ddrval = IDirectDraw2_Initialize(lpdd, NULL);
        }

        DDCAPS ddcaps;

        ddcaps.dwSize = sizeof DDCAPS;
        lpdd->GetCaps(&ddcaps, NULL);

        lpdd->Release();

        int iMem = ddcaps.dwVidMemTotal/1024/1024;

        CAPPLog::Log(LOG_INFO, _T("Total display memory is (%d) %d MB"), ddcaps.dwVidMemTotal, iMem);
        iMem = ddcaps.dwVidMemFree / 1024 / 1024;
        CAPPLog::Log(LOG_INFO, _T("Free  display memory is (%d) %d MB"), ddcaps.dwVidMemFree, iMem);

        CoUninitialize();
    }

notice:
我原样贴出了我在我们工程里面写的代码， 里面有个CAPPLog::Log是用来写log到某个文件的，直接改成_tprintf就可以直接用了。

reference:
http://blog.csdn.net/bohut/archive/2004/10/26/152234.aspx