Remote into Client desktop from Server

Hey guys. I have been pulling my hair out today over this issue. OK so i am the domain admin of a school. I already have access from the outside to remote into my server at anytime. However, i have a small issue. I would like to be able to remote into one of my clients domain accounts on his machine from time to time when hes having issues. I need to remote in directly to his machine. So I will lay it out here:

I logon remotely to my server into the domain
I then want to remotely connect to my clients machine and login to his domain account with his credentials. I pull up the RDP and put in his IP and credentials etc.
I get through to his machine with success however when i do, i get a message:

To log on to this remote computer, you must be granted the allow log on through Terminal Services right etc. etc.

Now i think where i went wrong is I followed online instructions and gave him rights for terminal services, remote access etc. but i did this on my server dc. I assume my issue is i need to give him these rights directly on his client machine?? What i mean is, do i need to be at his client pc and give these rights while im on his machine for this to eventually work ? I am stumped and any help is greatly appreciated. If more details are needed just ask and i will post more info

P.S. Domain Controller is Server 2008, Client PC is Windows 7