Code:

procedure TForm1.Button1Click(Sender: TObject);

var

ProcessID: DWORD;

ProcessHandle: THandle;

ThreadHandle: THandle;

begin

ProcessID := GetCurrentProcessID;

ProcessHandle := OpenProcess(PROCESS_SET_INFORMATION,

   false, ProcessID);

SetPriorityClass(ProcessHandle, REALTIME_PRIORITY_CLASS);

ThreadHandle := GetCurrentThread;

SetThreadPriority(ThreadHandle, THREAD_PRIORITY_TIME_CRITICAL);

end;