Windows Nashville build 999

Windows Nashville build 999 is the only leaked build of Windows Nashville from early 1995-12.

It contains Athena PIM (later released separately as Microsoft Outlook). The branding still says "Windows 95" in most places, except in Add/Remove Programs, where it says "Windows 96", and in the Command Prompt, where the  command reports "Windows Nashville".

Installation
Installation is similar to installing an upgrade version of Windows 95, but it doesn't always work and may BSOD during the second stage of setup. It's also worth noting that this build will not upgrade from Windows 95 if Windows 95 was installed on a FAT32 partition.