I'm running Windows XP Professional SP3 x86, trying to connect to a system with Windows 7 Ultimate SP1 x64.
Recently, I updated the Remote Desktop Connection software on the XP system in hopes of using Network Level Authentication (NLA) for my connections to the Windows 7 box. After the update, I connected to the Windows 7 box over RDP and enabled NLA believing that the updated client should support it.
After disconnecting and attempting to reconnect, I'm presented with the following error:
The remote computer requires Network Level Authentication, which your computer does not support. For assistance, contact your system administrator or technical support.
So, I checked the About page in Remote Desktop Connection to make sure the update had applied. This is what I see.
Remote Desktop Connection
Shell Version 6.1.7600
Control Version 6.1.7600
© 2007 Microsoft Corporation. All rights reserved.
Network Level Authentication not supported. Remote Desktop Protocol 7.0 supported.
I thought NLA was supposed to be a part of RDP 7.0 clients. Is there a component I'm missing somewhere?
Microsoft has a KB article on this:
http://support.microsoft.com/kb/951608
Specifically, XP doesn't have the right credential provider enabled to allow it. This credential provider, CredSSP, need to be turned on before NLA will work on XP-Sp3. The linked article has a 'Fix it for me' button, or if you'd rather do it by hand, there are a couple of registry settings that need to be entered. A reboot needs to happen for this to take effect.
You have to turn on the Credential Security Service Provider (CredSSP).
Click HERE to see how to.