Some of the latest versions of Windows have a command ‘shutdown.exe‘,which can put your system on hold, log off, restart, and shutdown. But probably you would want this to happen only at some particular time and to make this happen automatically use Scheduled Tasks tool.
1> Go to Control Panel > Scheduled Tasks.
2> Double-click Add Scheduled Task to launch the Scheduled Task Wizard.
3> Click Next and then click the Browse button.
4> Access the Windows\System32 folder, select Shutdown.exe, and click Open.
5> Follow the wizard through the next two screens to give the task a name and choose a schedule.
6> Enter your user account name and password and click Next.
7> Select Open Advanced Properties and click Finish.
In the task’s Properties dialog box, add the /r parameter to the end of the command line in the Run text box and click OK. (Be sure to include a space between the last character in the command name and the first character in the parameter list.)
Enter your user account name and password and click OK.
When the Shutdown utility runs, you’ll momentarily see a small dialog box on your screen before the system restarts.
The above process works fine, but there is an easier way to achieve this. Vista Shutdown Timer, is a simple application which allows users to achieve the same with ease. The auto shutdown process has a limitation. Scheduling cannot be done for more than an hour. With Vista Shutdown Timer this limitation can be used to overcome.
Vista Shutdown Timer is a free application that allows the user to time the machine to shutdown at their time. This currently supports support Windows 2000, Windows XP and Windows Vista. Another interesting feature is that Vista Shutdown Timer does not mess around with the registry and doesn’t introduce any .INI files, it is just a single .exe file.

The program can be configured using command line parameters. This means that we can create a batch file to automate the tool to shutdown or restart at a scheduled time. Click the windows icon at the top right of the program to know about the command line parameters. If this confuses you, use the built-in Shortcut wizard which is simple to use and hassle free.

Vista Shutdown Timer at times is flagged as a suspicious file by some antivirus software such as Sophos, QuickHeal, ClamAV, and eSafe. This happens for a lot of other applications even though the applications are safe and do not pose any threat to the users system. Such an alarm is called ‘False Positive’, which meant the anitvirus software is just throwing a warning of possible threat, which in reality is an innocuous file/application. This kind of incorrect flagging may be because the virus signature in the vault or database of the antivirus software may be corrected or not updated.
Related reading: Shutdown, restart, logoff windows Vista / XP remotely from any computer