RDP/Remote Desktop - Can't access other PCs in network

Right, I have a problem trying to externally remote desktop into a PC within an office network using Windows 7 Pro.

Ports have been open on the firewall/router for Remote Desktop and each of the PC's static IP addresses have been assigned for it to port forward to the Remote Desktop port. Also assigned are the users who are able to remote into their computers. All PCs are on and are also on Windows 7 Pro.

Unfortunately I can not connect to any of the PCs. I can however connect to the server with no problems and even connect to the other PCs using the Small Business Server 2008 control panel.

Is there anything else that's missing in setting up Remote Desktop that I haven't tried?

Maybe this tutorial will give you some ideas on what the problem might be.

Remote Desktop Connection (RDC) - Network

Thanks for the tip, but unfortunately, the PCs are part of a domain - so the part where I would have to change the registry would hinder Small Business Server 2008 to have the ability to remote desktop via terminal service inside the internal office network.

This was done before by one of our IT guys, but he's not back until next week and what I'm trying to do is rather urgent...