If you're a Windows Phone user, check your email -- you're about to get a big holiday treat. Microsoft has followed up its earlier Surface promo by giving Windows Phone owners a free 20GB of extra SkyDrive storage for the next year. The bonus capacity stacks on top of whatever is already present, and customers have until January 31st to claim their additional cloud space. You'll have to wait for an email like the one above before you can take action, but we'd expect these notices to roll out to all registered Windows Phone users in short order.