The Windows Remote Desktop client allows you to control a remote computer using the mouse and keyboard of your local machine. However, when you’re remotely connected to a computer and you press “Ctrl+Alt+Del,” the command affects the local rather than the remote computer. You must type a special key sequence to send the “Ctrl+Alt+Del” command to the remote computer.
Log into the remote computer from your local computer using Remote Desktop. The Windows 7 Remote Desktop client is located under “Start > All Programs > Accessories.” You will need the network address or name of the remote computer and a user name and password to log in.
Type Ctrl, Alt and End on the keyboard of your local machine. This will send the “Ctrl+Alt+Del” command to the remote computer.
Choose the option you want from the Windows Security dialog box, then continue working.