Disable Auto Reboot on Windows Updates

 When you updates via Windows Update manually or scheduled Automatic Updates automatically, system will auto-restart or auto-reboot in order to apply all the updates. Its almost same in Windows 7, Windows Vista and Windows XP, after installing downloaded. Though Windows 7 has added option to allow users to postpone or delay the restart, the computer will still automatically restart sometime later, if the updates required system to be rebooted to finish the installation.
After the installing of updates completed which requires to restart Windows, system will notify users that it needs to restart, and if there is no response from user in 5 minutes, Windows will automatically reboot the computer, even though user is logged on, and has programs running or documents opened. This result to lost any unsaved data, such as files, documents, spreadsheets, presentations, databases, and downloads or processes such as backup or defragmentation that not yet finished will be terminated.

We can prevent Windows from automatically restart. Just use the this trick to disable the auto restart after installing Windows Updates feature.

~Goto Start button and open Run, and type gpedit.msc to open Group Policy Editor.
~In Local Group Policy Editor, navigate to Computer Configuration -> Administrative Templates -> Windows Components -> Windows Update.
~Double click on No auto-restart with logged on users for scheduled automatic updates installations.
~Select Enabled radio button and click OK.
~Close GPEDIT (Local Group Policy Editor).

You can also add this directly in registry, in case of Windows 7, Vista and XP Home edition which does not have a Group Policy Editor.

~In Run type regedit to open Registry Editor.
~Navigate to the following registry key:
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\WindowsUpdate\AU

If the key does not exist, create new key and name accordingly.
~Change the NoAutoRebootWithLoggedOnUsers DWORD (32-bit) Value to 1 to disallow auto-reboot. By default, the value is 0 which allow auto-reboot.
If the value does not exist, create a new DWORD (32-bit) Value and name accordingly.
~Close Registry Editor.

After all above settings, Automatic Updates will wait for the computer to be restarted by any user, instead of causing the computer to restart automatically to complete a scheduled installation.