Often referred to as “the 3-fingered salute”, many users find it strange that they must press the Ctrl+Alt+Delete key combination when attempting to log on to a system running Windows XP Professional. This is because this key combination has been traditionally associated with forcing a system restart. On XP systems today, pressing Ctrl+Alt+Delete represents a special call to the security subsystem, that can display the logon window, task manager, and on XP Professional systems the Security dialog box.
In most cases, you are better off having the Ctrl+Alt+Delete key combination required and enabled for security purposes. To do so, open Control Panel and then click the User Accounts applet. If you click the Change the way users log on or off link in the Pick a task section and then uncheck the Use the Welcome screen checkbox (as shown below), all users will be forced to press the key combination prior to logon. Alternatively, this setting can be changed by firing up Regedit and creating a new REG_DWORD value called DisableCAD in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon. A value of 0 will require the Ctrl+Alt+Delete key combination, while a value of 1 disables the requirement.