Go to “Settings” -> “Extensions” and disable unwanted extensions. You delete them if you are absolutely sure, you do not need it.

If it still does not stop here, you computer must have been hit by bug, work, malware (malicious software).

Go to “Control Panel” -> “Programs” and look for applications, you never expected. Un-install it and restart computer.

Make sure you do not download files (movies) from un-reliable sites.