Build 5381.1 is an IDX/IDW (I Don't eXercise) compile disguised as a beta, but don't be fooled, it's not subjected to the same standards and quality checks as a beta or even CTP.
Size, filenames, and AutoCRC values of Build 5342:
x64 Edition: VISTA_5381.1_64bit_Main_Client_Staged_DVD_EN.iso; at 4,834.25 MB
x86 Build 1: VISTA_5381.1_32bit_Client_Unstaged_CHK_DVD_EN.iso; at 2,296.55 MB
x86 Build 2: VISTA_5381.1_32bit_Main_Client-Staged_DVD_EN.iso; at 3,347.84 MB
Features List
Size, filenames, and AutoCRC values of Build 5342:
x64 Edition: VISTA_5381.1_64bit_Main_Client_Staged_DVD_EN.iso; at 4,834.25 MB
x86 Build 1: VISTA_5381.1_32bit_Client_Unstaged_CHK_DVD_EN.iso; at 2,296.55 MB
x86 Build 2: VISTA_5381.1_32bit_Main_Client-Staged_DVD_EN.iso; at 3,347.84 MB
Features List