At work I have 3 monitors connected and when I RDP any of the computers on my Home Server the RDP window uses all 3. I only want it to use a single monitor.

In a normal RDP connection settings, this is the "Use all my monitors for the remote session" option.

Is it possible to disable the multimon setting in the RDP connections that Home Server creates in Remote Web Access?

It would seem to me that you found a "feature" in WHS 2011 RDP. In my experience with Remote Desktop Connection (default RDP, not a third-party RDP client like visionapp Remote Desktop), the Remote Desktop Connection (RDC) client retains the settings of the last successful connection.

For example, if I use RDC to connect to a server, and I set the connection to use 1024x768, and I successfully log into the server and then disconnect/log off, the next time I use RDC to connect to any server, it will default to 1024x768. On the other hand, if I change to 1024x768 from 1920x1080, but the connection fails, and then I close RDC, the next connection I attempt will default to 1920x1080. If I have a successful connection using "all available monitors," the next connection will also use all available (by default).

The remote connection options are available by selecting the "more computers" link once you've logged in to Remote Access. In there, there's a Remote Desktop connections options. You can select the screen resolution (full screen, 1024x768 and others).

It looks like if you select Full Screen, and you have multiple monitors, it will use all monitors irrespective of what your last successful session settings in RDC. The only way I could get it to stay on one monitor was to select a specific resolution, not Full Screen. I could not get it to behave otherwise.

That said, I think it's reasonably safe to say you found a bug. I did not see anything in the web-based remote desktop settings that allows you to specify which monitor to use.

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Matt Sawyer
Owner, Dojo North Software, LLC

HP EX490, 4GB, E5300, 15TB - Server 2012 - Sharing and Streaming
HP EX487, 4GB, E5300, 13TB - Server 2012 Essentials - Backups