[Besso]

А еще неплохо настроить порт
DCB       dcb;
HANDLE hPort;
....
hPort = CreateFile(_T("\\\\.\\COM1", GENERIC_READ|GENERIC_WRITE,
 0UL, 0, NULL, OPEN_EXISTING, 0, NULL);
BuildCommDCB(_T("96,n,8,1", &dcb);
SetCommState(hPort, &dcb)