Windows 3.0 build 55

Windows 3.0 build 55 is a pre-release build of Windows 3.0. It was leaked in 1990 as a preinstalled folder and was later found and shared by BetaArchive member The Distractor on 3 March 2014. The original installation media for this build remains to be found. A rebuilt disk set has been made by member WinPC, but it uses some files from the RTM build. This build is currently the earliest available build of Windows to use Program Manager, that replaces MS-DOS Executive.

Installation
You need to click Cancel when setup asks for Disk 3 for the second time, then click Ignore when it asks for. This build should be installed on top of MS-DOS/PC-DOS 4.0 for Real Mode, or Compaq's MS-DOS 3.31 for 386 Enhanced Mode.

Paintbrush warnings
When you run the Paintbrush program for the first time, it will display two warnings. The first one informs you that Paintbrush doesn't work well in low-memory situations, so you should run it under Standard or 386 Enhanced mode. The second warning talks about a bug where the contents of overlapping windows can end up in your drawing. It recommends you don't display other windows on top of Paintbrush to avoid this bug.

Cardfile mouse bug
After exiting Cardfile, the cursor disappears, but the mouse still works.