XenDesktop 7 Windows desktop system or Windows server system only shows up on one display although you are using a dual-monitor setup.
By default, the StoreFront server is configured to start the VDI on one display only. This is by design but you should be able to maximize to both monitors after the session has started.
You need to edit the file
web.config in the "StoreWeb" directory on your StoreFront server.
The default directory is:
After saving, your published desktop should expand over both screens.