How to Reinstall Ubuntu on Window 10

Step 1. Uninstall ubuntu
Open Command Prompt (Or Window PowerShell) and type

> lxrun /uninstall

Type "y" to continue: y


If you'd like to completely uninstall Ubuntu that including user account information, you can use /full option
> lxrun /uninstall /full



Step 2. Install Ubuntu


Type bash on Cortana search bar and click "bash"

After that, you will see the message like

"This will install Ubuntu on Windows, distributed by Canonical ..."