Windows 3.0 build 55

Windows 3.0 build 55 is a pre-release build of Windows 3.0. It was scene leaked in 1990 as a preinstalled folder and was later found and shared by BetaArchive member The Distractor on 2014-03-03. It is the earliest leaked build of Windows to include the Program Manager shell. 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.

Installation
You need to click Cancel when setup asks for Disk 3 for the second time, then click Ignore when it asks for HIMEM.SYS. 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. It works in 86Box, PCem, QEMU, Bochs, VirtualBox, VMware and Virtual PC 2007.

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.