AT&T's Mobile Transfer is now available for Windows Phone handsets, offering an easy way for Lumia 900 owners to swap their contacts (along with up to 2GB of photos and videos) onto their shiny new handset. The app has previously been available for iPhone, Android, and BlackBerry users, as well as for a selection of featurephones available from the carrier, making it almost certain that it will work for you.
The data is uploaded from your old device to AT&T's servers, and is kept there until you activate a new device. Once your new phone's up and working, you're given seven days to download your data before it's wiped — a good security measure, but you shouldn't mistake this for a backup service. You can grab your data as many times as you like within those 7 days, though, meaning that you can reset your phone a couple of times if need be. The app's available now from the Windows Phone Marketplace on your handset, should you want to give it a shot.