Images of an old prototype Sony Ericsson Windows Phone device surfaced on the weekend.

The images were posted on a Chinese messaging board and appear to show an old prototype Sony Ericsson device. The device is clearly marked with “prototype – not for sale” and is running a very early beta copy of Windows Phone 7. Microsoft originally named Sony Ericsson as a launch partner when it first unveiled Windows Phone 7 at Mobile World Congress. It has since been reported that the pair could not reach an agreement around Microsoft’s Xbox LIVE integration.

Sony Ericsson had originally planned to launch a 4″ screen device featuring a QWERTY slide-out keyboard. The project was subsequently scrapped but recent rumors suggest that Sony Ericsson may be planning a Windows Phone 7 device later this year. The leaked device, featured above, could hint at Sony’s possible form factor for a future Windows Phone device. Unfortunately as it’s only concept, we’ll never see this device in retail stores.