The system requirements for Microsoft Dynamics NAV 2015 have been updated in the MSDN Library. In the original version, the section for the Windows client contain misleading information about the supported operating systems. This was a bug in the way that system requirements are gathered and tested, and we have changed the process accordingly. We are fully aware of the confusion that the misleading information about only supporting 64-bit editions has caused.
The Microsoft Dynamics NAV 2015 Windows client supports both 32-bit and 64-bit editions of Windows 8.1, Windows 8, and Windows 7.
As always, the latest version is in the MSDN Library at the following location: http://msdn.microsoft.com/en-us/library/dd301054(v=nav.80).aspx.
The NAV UA team and the NAV Release Management team