Official support from Microsoft for Windows XP ended as of 8th April 2014.
Windows XP is now a historic operating system and as such does not support some of the more modern technologies out of the box. To get the school Remote Desktop system to work on Windows XP you will need to run the two fixes hosted at the following links:
The first update:
Download and install this. This package will upgrade the Remote Desktop client to version 7
The second update:
Enables CredSSP which is needed to authenticate to Remote Desktop. Run the “Fix It” file to do this automatically for you.
Once you have installed these fixes, run the remote desktop connection file as you normally would and you should be able to login to Remote Desktop. When you type in your username, ensure to leave the CCS\ in the username field as shown below.