Forget what you knew about syncronizing your content with your Windows Mobile phone, because in Windows Phone 7, everything is different. We already explained how Windows Phone 7 won't sync with Outlook and what you can do to get your email, calendar, and contacts synced with the phone. We also showed you the Zune desktop software that lets you manage the multimedia on your Windows Phone 7 device.
But more specifically, what video and audio files will Windows Phone 7 support? Unlike Windows Mobile, you can't just click and drag multimedia to your phone from your desktop. Also unlike Windows Mobile, you can't download an awesome third party multimedia player like CorePlay and expect everything to play. In Windows Phone 7, all multimedia syncing is done through the Zune software. That means that if Zune can play the file (sometimes after having to convert it), it'll play on your Windows Phone 7 device.
I did a test with three video file types: .mov, .avi, and .wmv. I added them to my Zune library, and within a few seconds, each was playable within the software. I then clicked and dragged the videos to my Windows Phone 7 device, and after the sync concluded, the videos were on the device and could be played, even the .mov file. But later, when I tried to sync another .mov and .avi file, they were unplayable in Zune, and thus I couldn't send them to the Windows Phone 7 device. See all supported video formats for Zune.
In terms of audio, I tried syncing a .wma and .mp3 file with my Zune library and then with the Windows Phone 7 device, and they played without trouble. See all supported audio formats for Zune.
So the rule of thumb for Windows Phone 7 multimedia will be the following: if Zune can play it, your Windows Phone 7 device can play it. The downside to this model is that you're subject to the whims of Zune software. You're not going to be able to install a third-party multimedia player when Windows Phone 7 launches, so some of the more rare video and audio file types won't be able play on your phone.