var
  StartUpInfo: TStartUpInfo;
  ProcessInfo: TProcessInformation;
  sa: TSecurityAttributes;
  Arguments, exepath, reason : String;
  startOK: boolean;

  ProcID: Cardinal;
  appPath: string;
begin
  appPath:= ExtractFilePath(application.ExeName);

  Arguments :='\myproc.exe param1;
  exepath:= appPath+ '\myproc.exe';

      with sa do
      begin
        nLength := SizeOf(sa);
        bInheritHandle := true;
        lpSecurityDescriptor := nil;
      end;

      FillChar(startupInfo, SizeOf(startupInfo), 0);
      startupInfo.cb := SizeOf(startupInfo);
      startupInfo.dwFlags := STARTF_USESHOWWINDOW;
      startupInfo.wShowWindow := SW_HIDE; //SW_SHOWNORMAL;
      startupInfo.lpDesktop := nil;

      try
        if CreateProcess(
          nil,
          PChar(exepath),
          @SA, @SA, false, NORMAL_PRIORITY_CLASS,
          nil,
          PChar(appPath),
          StartUpInfo, ProcessInfo) then
        begin
          ProcID:= ProcessInfo.dwProcessId;
          startOK:= true;
        end
        else
          Reason:= SysErrorMessage(GetLastError);