Ctrl+Alt+Del have been one of the rescue Key combos since the Windows Evaluation. And during succession of Windows it has changed the offers and functionality it provides to user.
In Windows 7 Ctrl+Alt+Del combo gives the following option
Start task Manager
However restrictions can be made on the above features using Group Policy Editor Setting. This setting may
Prevent users from locking the system
Prevent users from changing their Windows password on the
Windows Security dialog box (which appears when you press Ctrl+Alt+Del).
Prevent users from starting Task Manager
This setting disables or removes all menu items and buttons that log the user off the system.
Steps to disable any of the features:
Open Run Dialogue Box (Win + R) and type gpedit.msc
Navigate to Local Computer policy > User Configuration > Administrative Templates > System in left hand side pane.
Select Ctrl+Alt+Del Options setting
Select any of the setting you want to enable from right side pane. (Enabling a setting means disabling the feature)
Open it and enable it.
A Reboot is required for the above setting to take place.