One of Microsoft’s cornerstones of Windows Phone has been the partnership with Nokia. The company has brought unique design to the platform through its Lumia phones, particularly the Nokia Lumia 900, but with Windows Phone 8 and the lack of full support for Windows Phone 7 devices Nokia suddenly finds itself having to effectively restart with a new line of devices despite selling a million Lumia 900s.

Windows Phone 7.8 doesn't bring the full Windows Phone 8 experience because of the new hardware - Microsoft introduced multi-core processors and the new Windows NT Kernel, among other changes - but does bring the new start screen which allows for tiles to be resized into one of three sizes. That means when Windows Phone 8 arrives, the current user base will effectively be cast aside.

It therefore means there's probably going to be fragmentation across the devices, a problem consistently aimed at Google's Android mobile operating system because devices have widely different hardware. For Windows Phone developers, there are now two operating systems to consider.

In comparison, Apple introduces new versions of iOS and new models concurrently (such as iOS 6 and, probably, the next iPhone this fall). The company also ensures that the newer version of iOS supports older devices: the iPhone 3GS can run on iOS 6, though the Flyover feature in the new Maps apps won't work.

Microsoft seems to have attempted to prevent the fragmentation problem by setting minimum hardware requirements for OEMs. However, the software giant itself admitted two functionally different devices are going to be on sale. Nokia's Lumia devices will be seen as functionally inferior, and for a company that had to downwardly revise its quarterly forecasts, that's not an ideal situation. For Nokia employees that were skeptical over Nokia CEO Stephen Elop's decision to abandon promising operating systems such as Meego for the push towards Windows Phone, this could be a point of contention.

"What was once a battle of hardware ... has now become a battle of software," phone retailer Carphone Warehouse's COO - Graham Stapleton - said to The Telegraph. When consumers see current Windows Phone devices not getting the full Windows Phone 8 experience, questions may be asked. Questions that must be answered.