I made a brief video a week or two back about the HDMI not working on a television as I would expect. Simply put, plug and play on a 720p tv was causing issues. This video has caused much debate so here is a more in depth video.
VGA connection is analog, and is different from HDMI connection (digital). In my experience, you're pretty much limited to 720p and 1080p for HDMI. As mentioned, Metro requires 1024x768 minimum (and 1366x768 for snap). Ask any netbook (1024x600) owner.
The solution would be to either swap out the large display for a 1080p model, or continue using it as an extended (2nd) display.
To move apps between displays (using "extended" display setup), suggest trying Winkey+PgUp/PgDn as mentioned in this link,
Time to eat some humble pie. I'll take 60-80% of the blame for this. HDMI cable was 'apparently' in the wrong port - though I hasten to add the Transformer Prime was always plugged into this port.
Grats on getting it to work. I have three questions.
1. From your YouTube video, it looks like it stretches the square TV picture onto the monitor. Is this true? It's a pet peave of mine to see $1000's of "high resolution" new tech with better picture quality, blah blah blah and then we are all forced to watch videos and pictures with people's faces stretched giving us the impression that every show is an off-shoot of "The Biggest Loser". Is this how the HDMI out on the Surface shows pics, vids, etc?
2. Does the Surface recognize and work with ad-hoc networks? Specifically for WiFi tethering with a smart phone?
3. Does the Surface's IE notify smartphone networks when tethering to bring up the "You must pay $$$ for HotSpot" window? Or are there other options for browsing the internet with Windows RT?
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?