I have a SBS 2003 server with Terminal Services enabled. Currently I am able to RDP to my server by going to www.mydomain.com. I would like to restrict RDP access to my network to be over VPN only. However, I am worried I will accidentally disable RDP to my server completely. How can I configure remote access to only be available when connected to a VPN?
Assuming you want to make that happen only from the outside (Internet), then simply do not allow RDP (3389) through the firewall. They would connect via the VPN, get an internal IP address, and then use the internal IP, or internal DNS, name of the server to connect.
Just create a firewall rule to only accept RDP connections from whatever IP address range your VPN users get.