I've just got a Dell P2314T touchscreen monitor (1080p) and have connected it in place of my old Dell ST2220M (1080p), as a secondary to my Dell U2412M (1920x1200).
However, when I set it to 1920x1080 it only fills about 20" of the 23" screen, leaving a large border. I tested with a few resolutions and none of them fill the screen. If I boot into Windows 7 however, it fills the screen normally at 1080p. I had a look at Catalyst Control Centre and that looks the same in Win7 and Win8, showing under Desktop Properties all resolutions up to 1680x1050 under Basic and higher resolutions under HDTV. The U2412M doesn't separate them like this but that's probably because it's connected via DP.
The other problem is that when I touch the touchscreen, it moves the cursor or scrolls the webpage on the other screen. If I go to Control Panel - Tablet PC Settings, it says that the U2412M has "Full Windows Touch Support" (it doesn't) and for the P2314T it says "No Pen or Touch Input is available for this display". If I click Setup, which prompts me to touch the screen if it's the touchscreen or press Enter if not, I do this to get the prompt on the P2314T and touch it (which shows a pulse on the U2412M) but it doesn't change what it shows under Tablet PC Settings or what happens when I try and use the touchscreen. I tried this under Windows 7 as well and had the same result.
Anyone know how to sort either or both of these problems out, so that I can play with my new toy over the weekend?