When you press [Ctrl]+[Alt]+[Delete] together,you get a new Window which has following Options:
*Lock this computer
*Switch User
*Log Off
*Change a password
*Start Task Manager
You can remove any of the above options, except Switch User as follows:
1.Go to Start Menu Search box, type gpedit.msc and hit enter.
2.Head to Administrative Templates > Network > System
3.Select Ctrl+Alt+Del Options
4.On the right site pane right click on any of the items, select Properties and check the box named 'Enabled'.
5.Press Apply.
6.Logoff and log on the system to see the change.
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