Downloading open source (the unix variety) means that you end up having a folder called DOC with a bunch of plain-text files that have no extension
Windows doesn't really know what to do with that, because it uses the extension (whats after the last dot) to assign a mime-type and associate default shell commands.
Sometimes you want to rename those files to reflect that they're plain-text ascii files so you can open it with notepad (and friends)
open your shell, and run the following after changing your working directory to the afore mentioned DOC folder
for /f %i in ('dir /b') do @rename %i %i.txt
bitchin'