Do you mean you want it to go to sleep on a schedule? For example, setting your computer to go to sleep at 10:00 PM each night? Or do you just want to be able to have it go to sleep on a time from when you go afk? If it's the second option you want, all you need to do is change your power settings in windows 7 to put the computer to sleep after x amount of minutes. Just search for "Edit Power Plan" in you windows start menu, and choose than option. You should be able to set your current power plan to put the computer to sleep after a time that way.