The proper avenue to get this is from the maker of your PDA or Phone. I can't discuss any other method and Microsoft doesn't sell it. The reasons why are widely discussed so I don't duplicate that either.
In short, ask ATT.
I have an At&t Tilt with Windows Mobile 6.0 Professional.. I have seen a bunch of leaked Windows Mobile 6.1 videos on Youtube. When will this be coming out? Does anyone know if it will be a free upgrade or will I have to purchase it?
This appears to fill in a lot of the holes that may lead others to the iPhone. I mean the Tilt has a camera, touch screen, GPS, WiFi, Bluetooth 2.0, 3G, back lit QWERTY keyboard and is an open platform where I don't have to hack it or wait to put programs on it because they already exist... Why do people want the iPhone again?