Are you looking for a small tool which can help you in shutting down your system after a specified interval of time, then try WinDown. It is a portable light-weight tool which lets you shutdown your system after a specified time.
Simply set the time upon which you want the system to shutdown and click the Start button. It will get minimized to the system tray and will shutdown your system on the specified time.
We have already reviewed some tools which provide the same functionality, you may read one such post here. The one of the benefit of this tool is that it does not have many options, which makes it simple and very light-weight (I found it consuming hardly 1/4 MB of memory). It works perfectly on all modern versions of Windows like Windows XP, Vista and Windows 7. Enjoy!