[RESOLVED] One thread stop all system!! How avoid it? :(

Windows 7. Only mouse work and the thread.
What incorectly??

Code:

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WriterThread = (HANDLE) _beginthread(Writer, 0, NULL);

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Code:

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void Writer(void *args)
{
  Writing = TRUE;
  Stop    = FALSE;
  HANDLE hf;
  HWND hProgress = CreateWindowEx(0, PROGRESS_CLASS, NULL,
                              WS_CHILD | WS_VISIBLE,
                              20, 20, 260, 17,
                              hwnd, NULL, hInst, NULL);
 
  if (InitPort())
  {
        MessageBox(hwnd,L"asdfasdf", L"asdf", 0);       
        Writing = FALSE;
    return;   
  }
  hf = CreateFile(FileName,         
                    GENERIC_READ,
                    0,
                    (LPSECURITY_ATTRIBUTES) NULL,
                    OPEN_EXISTING,
                    FILE_ATTRIBUTE_NORMAL,
                    (HANDLE) NULL);
  if (hf == INVALID_HANDLE_VALUE)
  {           
        MessageBox(hwnd,L"asdf", L"asdf", 0);       
        Writing = FALSE;
    return;       
  }
  DWORD sz    = GetFileSize(hf, NULL); // asdfasdf
  unsigned CycleCount = sz/(256*20);
  SendMessage(hProgress, PBM_SETRANGE, 0, MAKELPARAM(0, 20));
  DWORD tmpBytesRead;
  DWORD Written;
  int szName = strlen(TempName);
  if (!WriteFile(hComPort, TempName, szName, &Written, NULL))
      {           
            MessageBox(hwnd,L"asdf", L"Ошибка", 0);       
            Writing = FALSE;
        return;       
      }
  if (!WriteFile(hComPort, &STX, 1, &Written, NULL))
          {
            MessageBox(hwnd,L"asdf", L"asdf", 0);       
                WriteFile(hComPort, &Eof, 1, &Written, NULL);
            Writing = FALSE;
        return;
          }
  int ProgressPos = 0;
  unsigned Index = 0;
  int CycleIndex = 0;
  char buff[256];
  int ReadSize = 256;
  while (Index < sz)   
  {
    SendMessage(hProgress, PBM_SETPOS, ProgressPos, 0);
        CycleIndex++;
        if (CycleIndex == CycleCount)
        {
          CycleIndex = 0;
          ProgressPos++;
        }
    if (Stop)
        {
          WriteFile(hComPort, &Eof, 1, &Written, NULL);
          Writing = FALSE;
          CloseHandle(hf);
          CloseHandle(hComPort);
          return;         
        }
    if ((sz-Index) < 256) ReadSize = sz-Index;
    if (!ReadFile(hf, buff, ReadSize, &tmpBytesRead, NULL))
        {
          MessageBox(hwnd,L"asdf", L"asdf", 0);       
          WriteFile(hComPort, &Eof, 1, &Written, NULL);
          Writing = FALSE;
          CloseHandle(hf);
          CloseHandle(hComPort);
          return;
        }
    if (Stop) // asdf
        {
          WriteFile(hComPort, &Eof, 1, &Written, NULL);
          Writing = FALSE;
          CloseHandle(hf);
          CloseHandle(hComPort);
          return;         
        }
    if (!WriteFile(hComPort, buff, ReadSize, &Written, NULL))
        {
          MessageBox(hwnd,L"asdf", L"asdf", 0);       
          WriteFile(hComPort, &Eof, 1, &Written, NULL);
          Writing = FALSE;
          CloseHandle(hf);
          CloseHandle(hComPort);
          return;
        }
        Index = Index + ReadSize;
  }
  WriteFile(hComPort, &Eof, 1, &Written, NULL);
  Writing = FALSE;
  CloseHandle(hf);
  CloseHandle(hComPort);
  MessageBox(hwnd,L"asdf", L"asdf", 0);
  return;
}

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Strange. It was only one time. But main window isn't active. This is trouble.

I added Sleep. Now it such as work.