Step 1: Open Task Manager
Step 2: Click on Performance
Step 3: Check whether Virtualization is enabled
If it is not enabled, restart your system and keep pressing esc button and inside you will be able to find place where you can enable virtualization.
Also, there is one more very important step after Docker is installed. That step is to open the Docker Quickstart Terminal by doing a right click and Run as administrator (make sure you do that every time you open Docker).
If there are any issues with Docker installation. Then un-installation should be done properly. Even if a single old file is left in C drive, it could create trouble. To solve this problem, you can install Revo uninstaller software to uninstall Docker.