Windows 95 build 28

Microsoft Cougar build 28 is a fake Windows build, supposedly part of the Cougar project which was said to predate Chicago. The build itself is just a modified Windows for Workgroups 3.11, while the Cougar codename was actually used for the 32-bit protected-mode kernel introduced with Chicago and not an entirely separate OS. However, it is possible that Windows for Workgroups 3.1 was initially forked into Cougar for the sole purpose of developing the new kernel, before it was merged into the Chicago project. Thus, builds of Microsoft Cougar with a new kernel but old shell could potentially exist.

According to the NFO file included, it was leaked by Battler (at the time known as OBrasilo) on the Euro-Asian Beta Group in 2008. It can still be found online to this day.

NFO file
NFO contents