The official instructions for installing the windows Subsystem for Unix-based Applications list two steps:
Open the "Turn Windows features on or off" window and turn on "Subsystem for Unix-based Applications."
Download and install the USA Utilities and SDK.
I'm stuck on step 1. The windows features dialog box on my Windows 7 Pro x64 system doesn't list SUA at all! None of the official or third-party instructions I've found address this possibility.
Here's a screenshot showing on the left, an image from the installation tutorial video, and on the right, my own system. Notice no "subsystem" on the right.
If all else fails I could use Cygwin, but I wanted to try out this alternative.