Codex might be the first glimpse of a working Courier-like prototype. Although it's bulky and unrefined, it proves the concept is workable. Another plus to the Codex is that it actually exists.

Dual screens are oriented automatically by sensors to provide the correct configuration based on the activity. The hinge in the center allows Codex to close, stand upright, and open in a variety of positions. Two people could use the device simultaneously.

Courier has been discussed, rendered and conceptualized, but the actual device remains to be seen. Whether the hardware exists or not, sources inside Microsoft are already indicating the company plans to release the product sooner rather than later.

Mary Jo Foley at ZDNet has inside sources at Microsoft who say the company wants Courier to hit the market in mid-2010. Considering that Courier is not even in the commercialization pipeline yet, that could be an ambitious goal.

Several Courier prototypes are said to exist, although the exact number is unknown. The device is rumored to be at a stage in product development where user interface concepts are being circulated to outside agencies. What about the hardware?

According to Mary Jo Foley at ZDNet, the product is an "incubation" project, which puts it one step ahead of a "research" project. Her sources have also indicated that when it hits the commercial pipeline Microsoft will manufacture the device itself.

Sources have told Mary Jo Foley at ZDNet that the Courier dual-screen tablet will run Windows 7, Microsoft's latest operating system. However, standard Windows 7 applications will not run on Courier.

Applications will be specifically tailored to take advantage of the touch-screen capabilities and unique display configuration of Courier. This way Microsoft can insure that the user experience on Courier is optimized for the hardware.

Renderings of Microsoft's Courier have leaked to Gizmodo. The images show the dual-screen device powered up, looking finished and portable. Pioneer Studios, a division of Microsoft Entertainment and Devices, has developed a series of internal Courier concept presentations. Here are renderings of the device and stylus.

Microsoft Courier will have two seven-inch screens and close like a book. Users interact with the tablet using a stylus or by touching the screens.