As I understand it...Windows Defender may display this message when the user has Microsoft Security Essentials installed (which has an antispyware function).
IMO, a better alternative to using Windows Defender would be installing SUPERAntiSpyware and Malwarebytes. SAS has daily updates and is generally consdiered to be one of the more efficient alternatives for minor malware items, while Malwarebytes is considered to be very effective against various malware items. There is no one program that protects the system against everything, hence the suggestion to use the two programs suggested, along with your installed AV program and a firewall.
I'm certainly no expert of any sort...just a user who has tried many of the products which users will believe to be effective.
Ad-Aware has long been considered to be inferior to the programs I have suggested.
Malwarebytes.org - http://www.malwarebytes.org/mbam.php
SUPERAntiSpyware - http://www.superantispyware.com/superantis...efreevspro.html
. Be sure click the button for the free download, not the other.
As with any program, please read all instructions for using...before installing.