This are the Developer Previews (not the public beta) of Mac OS X. This versions of the system were launched between May 1999 and May 2000, only for developing purposes.
In DP1 and DP2, OS X looks very similar to Mac OS 9, but it still have OPENSTEP elements. With DP3, Apple introduced the first version of Aqua, which evolved with every new beta version of the OS.
You can find more screenshots at http://www.guidebookgallery.org/guis/macos/macosx
Thanks to WinWorld for upload this OSes!Compatibility
64 MB of RAM, 1 GB of HDD, G3 processor