In Remote Desktop Connection, server authentication verifies that you are connecting to the correct remote computer, or server. This security measure helps prevent you from connecting to a different computer or server than you intended and potentially exposing confidential information.
The strength of the verification required to connect is determined by your system security policy, which is set by your system administrator. If the actual verification does not meet minimum policy requirements, then you have three available authentication options:
Connect and don't warn me
With this option, even if Remote Desktop Connection cannot verify the identity of the remote computer, it connects anyway.
With this option, if Remote Desktop Connection cannot verify the identity of the remote computer, it warns you so that you can choose whether to proceed with the connection or not.
Do not connect
With this option, if Remote Desktop Connection cannot verify the identity of the remote computer, you won't be able to connect.
If you're not sure which option to choose, ask your system administrator or the owner of the remote computer.
Remote computers that are running Windows XP or Windows Server 2003 or earlier operating systems cannot provide their identity for verification. If you know that the remote computer is running one of those earlier operating systems, you can avoid authentication warnings by choosing Connect and don't warn me, but be aware that this option is less secure than the other two.
If you want to permanently change the server authentication option, you can save your settings for that remote computer to an .rdp file (a file that contains all the settings for a connection to a particular remote computer). To do this, in Remote Desktop Connection, select the authentication level you want, and then, on the General tab, click Save or Save As. To connect to the same remote computer in the future, double-click the .rdp file.
If you have not yet installed Windows Vista Service Pack 1, you will see the following options instead:
Always connect, even if authentication fails
Warn me if authentication fails
Do not connect if authentication fails
For more information about installing Windows Vista Service Pack 1 (SP1), see Learn how to install Windows Vista Service Pack 1 (SP1).