you can use Task Scheduler to automatically launch applications and therefore use it to shut down Windows at a specified time?
And if your PC powers down when you shut down Windows, Task Scheduler can automatically turn off your system as well.
download exits 95/98 (should also work on XP) click here
1. Run the setup program you downloaded by double-clicking its icon.
2. Once the install is complete, open the Scheduled Tasks Folder by double-clicking Task Scheduler in the System Tray.
3. Using My Computer or Windows Explorer, find Exits95.exe in the Windows folder and drag it to the Scheduled Tasks folder.
4. Right-click the new Exits95 task and select Properties. In the "Run" box, alter the text to read C:\windows\EXITS95.EXE /n.
5. Choose the Schedule tab to specify when you want Windows to shut itself down. Click OK.
To test the Shut Down task, save any work you have open on your desktop, right-click the Shut Down entry in Scheduled Tasks folder and choose Run.
You can modify this job to protect your computer from premature shutdowns: Go to the Idle Time options on the Settings tab of the task's Properties dialog. Check "Only start the scheduled task if computer has been idle for at least xx minutes" and alter the given time frame.