I think it downloaded files, but it fail making symlink.
Code:
c:\buildslave\steam_rel_client_win32\build\src\common\symlink.cpp (56) : Assertion Failed: symlinks on windows require admin rights, only work on Vista and above, and aren't supported in client builds
Error! App '90' state is 0x602 after update job.
Files locate in ...steamapps\downloading\
But what @Mordekay said, use it in Linux, virtual machine.