If I am correct you are using windows 10 (64-bit). This is one issue which came after update of Windows 10.
You can re-install the Ubuntu with later version. For example: -
If you get the error while running - $ sudo apt-get update
Enter the following command to fix the issue - $ sudo rm -r /var/lib/apt/lists/*
Run the $ sudo apt-get update command again.
Hope this helps.
Thanks for your replies.