Last month TechCrunch reported this in an article titled A First Glimpse Of Chrome OS In The Flesh that features a number of screenshots.
This early version of Chrome OS, which was obviously not intended for the general public, installs on computers running Linux. The following video was recorded by the owner of Chrome OS Blog and shows how he got it to run on a computer running Ubuntu (one of a number Linux ‘distributions’).
Video of the leaked Chrome OS
Looks familiar? If you have tried Google Chrome browser you will notice little difference between the two versions.