You may have picked up a piece of malware somewhere. malwarebytes anti-malware is a free product that will scan your hard drive and get rid of things like that, if your current virus software is not up to the task. You might need to start your computer in 'safe mode with networking' before trying to download it. (Press f8 while the computer first boots up and choose that from the list you are offered) It is the malware itself that is popping up the message you are sseing, so don't do anything it wants you to do!