Available to download for free from the Windows Store, the new app allows easy sharing of content between the Windows 8 and Windows Phone 8 operating systems.
The app automatically saves photos and videos taken on a phone to a Windows 8 or Windows RT PC, laptop or tablet device.
"Your computer and your Windows Phone 8 work together seamlessly with the Windows Phone app so you always have your photos, videos, and music, and more where you want them," Microsoft said.
The app is useless at the moment as smartphones running Windows Phone 8 have not yet become available.
But Microsoft will hold a Windows Phone 8 launch event in London tonight, where it will showcase the new operating system and the devices that will run it, such as the signature HTC Windows Phone 8X
The software includes various new features, including resizable 'live tile' homescreen icons, support for multi-core processors and high-res screens, and integrated NFC support.
Windows Phone 8 smartphones are expected to go on sale next month.