I am building a new HTPC for my son who is disabled. He needs a touchscreen monitor and an HDTV. I want to be able to control the software from the touchscreen and view content on the TV. The machine will be running Win 8.1 and I was originally planning on using XBMC. However, I have recently seen posts suggesting that XBMC doesn't play nicely with two screens. Is this true and what software would be better suited?
Unfortunately, I don't have any experience in a set up like you're looking for. I think some of the older HTPC cases with built-in monitors (5" - 7" screens) would probably do something like what you're looking for
While I haven't actually tried it in Windows 7 (or 8/8.1), I remember in XP that even using a cloned, dual monitor set up, if you selected full screen multimedia play-back, one screen would display it while the other would go blank.
If you son still has the use of his thumb(s), I think an HTPC remote would be the best option for him.
I use VLC on a two monitor setup and full screen on my main monitor still leaves my secondary available for browsers/email/etc by setting extended desktop, but I'm running 7/64. I had liked XBMC as it has a rather snazzy android remote app which would suit him down to the ground and he needs a friendly library functionality. My experience of VLC is that it requires a knowledgeable guiding hand. The real difficulties I am envisioning are that his TV will be the secondary monitor and he wants to retain use of the primary (touchscreen) during playback so it has to be extended desktop like my setup. I imagine the blanking is down to DHCP requirements on the HDMI connection. My primary monitor is on DVI and second on VGA, but his primary will (I believe) need DP for the touchscreen with the TV on HDMI or DVI>HDMI to get 4:4:4 chroma sub-sampling. Please correct me if that is wrong.