This build is the fourth developer release of Windows ME. It is referenced in "The Road to Gold: The development of Windows Me" at Paul Thurrott's SuperSite for Windows. According to Thurrott, it introduced a new shutdown splash with a 'Beta One' graphic which can be viewed here. However, the screenshot could also be of another build such as 2368. This build was released on 24th August 1999. This build is referenced in several serial number websites, but hasn't been found yet and thus can't be confirmed to exist.