Tufour is a project to use the Xbox 360 as a thin client for various platforms by using the Media Center Extender functionality built into it.
I'm currently working with the lead developer of xrdp to tweak it so it's compatible with the dialect of RDP that the Xbox 360 uses. Until this part is finished, it won't be possible to get the Xbox 360 to actually connect to a session on the remote computer.
That said, if you're excited by key exchange and connection setup, then you can download the pieces I've got already. It's a CLI executable and runs on both Microsoft's .NET framework and Mono. The source code is available through SourceForge.
You'll need a couple of things:
Tufour.exe accepts a single command-line parameter: the setup key generated by the Xbox 360.
Project IRC channel is #tufour on Freenode.