I have been asked to admin the server of a small business located in another city. The server is basically a Windows XP Pro PC being used as a file server for the 4-5 workers in the office, and I'll need a way to access it remotely... but also securely; in other words, I really don't like the idea of leaving any RDP/VNC/whatever service wide open to the entire Internet.
After having a quick look at the server, I noticed that the previous admin had Team Viewer installed on it, but I have no idea of whether the business has the proper licenses for it (small business, no IT staff... you know how it goes). In principle, I'd prefer to use it, since I like the fact that it uses TeamViewer's own servers to route traffic, which means that I'd have to open the firewall only to TeamViewer's servers. However, I don't know whether I'll be able to use it...
...Which brings me to Remote Desktop. I have read this answer about how to tunnel RDP over HTTPS, but it depends on a new feature in Windows Server 2008, so I can't use it. Is there any other way to secure RDP access, considering my constraints? (mostly: Windows XP as server). Any other software that might be useful?