HRESULT __fastcall AnsiToUnicode(LPCSTR pszA, LPOLESTR* ppszW) { 
    ULONG cCharacters;
    DWORD dwError;

    // If input is null then just return the same.
    if (NULL == pszA)
    {
        *ppszW = NULL;
        return NOERROR;
    }

    // Determine number of wide characters to be allocated for the
    // Unicode string.
    cCharacters =  strlen(pszA)+1;

    // Use of the OLE allocator is required if the resultant Unicode
    // string will be passed to another COM component and if that
    // component will free it. Otherwise you can use your own allocator.
    *ppszW = (LPOLESTR) CoTaskMemAlloc(cCharacters*2);
    if (NULL == *ppszW)
        return E_OUTOFMEMORY;

    // Covert to Unicode.
    if (0 == MultiByteToWideChar(CP_ACP, 0, pszA, cCharacters,
                  *ppszW, cCharacters))
    {
        dwError = GetLastError();
        CoTaskMemFree(*ppszW);
        *ppszW = NULL;
        return HRESULT_FROM_WIN32(dwError);
    }

    return NOERROR;
}