Hi jampatana,
u can use the inbuild windows command to do the job.
1) Open notepad.
2) type "shutdown -s -f -t 60"
3) Save the notapad by any name.bat (e,g, XXXX.bat)
4) Go to scheduled tasks in control panel & add a new scheduled task, on the second prompt, click browse and located the XXXX.bat file.
5) follow the wizard and configure it to run at the time u need to shutdown ur system.
For any clarifications get back to me.
ALL THE BEST