Unroot Google Nexus 7

1. Install Nexus Root Toolkit
http://www.wugfresh.com/nrt/

Select Appropriate Device and Software (Nexus 7v1, Androi 4.2)
Waiting for downloading some .img from Google

2. Install Nexus success


3. Click Full Driver Installation Guide 
Check driver installation steps + install adb interface.

4. If Full Driver Test is failed
Back to Step 2 to install Driver 2 instead of 1

5. Unlock Bootloader (Not unlock network operator)

6. Root