How do you remove doubleclick?

Check the hosts file in your computer and remove any suspicious entries (if any). To do it go to:

C:\Windows\System32\Drivers\etc\hosts

Make sure you open the two files (hosts file and hosts backup) with Notepad.

Doubleclick is a group of cookies that keep track of your browsing habits so it can later use it for advertising matters.

Anyways, they are not that dangerous, but rather annoying. Know that they might become harmful if its connected with cyber criminals.