Windows 8.1 Update (KB2919355)
http://support.microsoft.com/kb/2919355

64-bit (x64):  http://www.microsoft.com/en-us/download/details.aspx?id=42335
32-bit (x86):  http://www.microsoft.com/en-us/download/details.aspx?id=42327


KB2919442 (http://support.microsoft.com/kb/2919442) is a prerequisite for
Windows 8.1 Update and should be installed before attempting to install KB2919355


Install Windows 8.1 Update (KB2919355) files in the following sequence:
  clearcompressionflag.exe
  KB2919355
  KB2932046
  KB2959977
  KB2937592
  KB2938439
  KB2934018