I honestly don't know if this just a Vista thing or not, but I have the game installed on another computer of mine and in the video settings, there is no option for high quality. It goes only says Low and Medium on the main setting, as well as on the Sub sampling option. The specs are above minimum (I upgraded it specifically for my friend to play ESO on), and the GPU that I used to play on a High/Medium mix when it was in my main computer (Win 7) is now in the Vista, so I know it can handle at least that much. All drivers on the Vista are up to date to my knowledge. My game on the Win7 has the option for and is being played on high settings most of the time with a new GPU.
That said, medium quality isn't that bad, just a bit blurry. It's certainly WAY better than when he was trying to play on his poor laptop. I just don't know why the option for high isn't available. The game takes a long time to load in sometimes- 5+ minutes-, which I attribute to a bottleneck in his very outdated hard disk's speed (I can't afford to get a new hard drive and new OS key at this time). I could be wrong, though. I'm not a computer expert. The hard disk may not have anything to do with anything at all.
Edited for clarity, sorry.
Edited by Eorea on July 18, 2014 4:24AM