Recent versions of the Windows Remote Desktop client contain features not found in previous versions, including Network Level Authentication, which increases the security of the Remote Desktop connection. This feature was introduced in version 6 of the Remote Desktop (also called Terminal Services) client. Determine the version of the Remote Desktop client installed on your computer by examining the executable file.
Click the "Start" button, then click "My Computer" in Windows XP or "Computer" in Windows Vista or 7.
Browse to "C:," "Windows" and "System32."
Right-click on the file "mstsc.exe" and click "Properties."
Click the "Version" tab if you are running Windows XP or the "Details" tab in Windows Vista and 7. The version of the Remote Desktop client installed on your computer is shown next to "File Version" in Windows XP or "Product Version" in Windows Vista and 7. The version number will be long--for example, 6.1.7600.16385.