DWORD /*dwThreadId, */dwProcessId; // This is bad habit to keep commented code in your sources. The commented variable should be removed.

// Just keep
DWORD dwProcessId;

// The same thing here...
/* dwThreadId = */GetWindowThreadProcessId(reinterpret_cast<HWND>(hWnd[i]), &dwProcessId);

// Stay with:
GetWindowThreadProcessId(reinterpret_cast<HWND>(hWnd[i]), &dwProcessId);



// -----------------------------------------------
DWORD state = ::WaitForSingleObject(hProc, timeout);

// Why not auto? You will do not need to remember the type returning by WaitForSIngleObject...
auto state = ::WaitForSingleObject(hProc, timeout);



// -----------------------------------------------
if ((state == WAIT_TIMEOUT) || (state == WAIT_FAILED))
      	ret = ::TerminateProcess(hProc, 0); // You have space indentation instead of tabs... 



// -----------------------------------------------
//bool hdSerialMatch = false; // The same problem with commented code - not used remove it.