Authentication Validation Error When Connecting to Windows XP

If Windows XP is installed on your PC, when trying to connect to a remote desktop of the server, you can see the message like:

"The remote computer requires Network Level Authentication, which your computer does not support. For assistance, contact your system administrator or technical support."

To resolve this issue:
1) Check to see if you have SP3
2) Check if you are using the latest version of RDP client:
http://support.microsoft.com/kb/969084
3) Execute this reg. file on your PC with Windows XP: https://serverdale.com/download/CredSSP.rar (first unarchive it). Then restart your PC.