Prerequisites:
Pull "Download Assistant" for Unity 5.6.0b3.

Steps to repro:

1. Launch "Download Assistant" for Unity 5.6.0b3 on Windows 8 or higher;

Actual result:
"Unity requires Windows 7 or later" error is shown when installing documentation. See attached screenshot.

Expected result:
Installation finishes without errors on Windows version 7 or higher.

Notes:
- Reproducible in 5.6.0b3; not reproducible in 5.6.0b2;
- Also happens when installing WebGL platform;
- On OSX error 'Unable to download component' is shown, though it may not be directly related to this bug.