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Windows Vista introduced a new group policy: Delete user profiles that are older than a certain number of days when the system is rebooted.
This policy setting allows an administrator to automatically delete user profiles that have not been used within a certain number of days after accessing a specific user profile when the system is restarted. You may need to do this if you are working in an environment where many users come, creating a user profile, using the system for a while and leaving – such as an educational institution or a workplace – and you do not want unused user profiles to clutter up your system.
To configure this setting, enter gpedit.msc in the start search and press Enter to open the Group Policy Editor. Then, under Computer Configuration, expand Administrative Templates > System > User Profiles.
Double-click in the right pane to navigate to Delete user profiles older than a certain number of days when the system is restarted to open the configuration box.
If you enable this policy setting, the User Profile service will automatically delete all user profiles on the computer that have not been used within the number of days specified the next time you reboot the system.
If you disable or do not configure this policy setting, no profile will be automatically deleted the next time you reboot the system.
According to some reports, an error in the User Profile service could result in unexpected deletion of all user profiles after deleting the User Profiles setting that were older than a certain number of days when the group policy was restarted on a Windows Vista computer. You can play it safe and see if you need to apply this patch to KB945122. Of course, if you have the latest Vista Service Pack installed, there’s nothing to worry about.