求教Createfile函数在MFC中的使用？

这个是我再控件上添加的响应函数
UpdateData(TRUE);
    int j;
    unsigned char buf[512];
    OVERLAPPED overlap;
    HANDLE hFile = CreateFile(_T("\\\\.\\PhysicalDrive0"),//打开磁盘
                         GENERIC_READ|GENERIC_WRITE,
                       FILE_SHARE_READ,
                       NULL,
                       OPEN_EXISTING,
                 0,//FILE_FLAG_OVERLAPPED,
                       NULL);
    DWORD RSize=0;
    overlap.OffsetHigh = (DWORD)( 63*512ull / 0x100000000ull );//读取磁盘的偏移
    overlap.Offset     = (DWORD)( 63*512ull % 0x100000000ull );
    ReadFile(hFile, buf, 512, &RSize, &overlap);//读取磁盘
    CloseHandle(hFile);
    for(j=0;j<512;j++)
    {   
        CString buf1[1000]={0};
        if(buf[j]/16%16==0)
        {
            buf1[j].Format(_T("0%X "),buf[j]);
            if((j+1)%16==0&&(j+1))
            {
                buf1[j].Format(_T("0%X"),buf[j]);
            }
        }   
        else
        {
            buf1[j].Format(_T("%2X "),buf[j]);
            if((j+1)%16==0&&(j+1))
            {
                buf1[j].Format(_T("%2X"),buf[j]);
            }
        }
        m_sector+=buf1[j];//将数据赋值给控件上添加的局部变量
    }   
    UpdateData(FALSE);
但是在调试的过程中发现打开磁盘读取时buf数组赋值完全不正确全部都是CC，想请问一下是哪里出了问题？
调试的截图如下：