Try to start WD in Control Panel>Adminstrative Tools>Services.

"Rishi" <rishianitstigma******.com> wrote in message
news:220373c2-34e2-4b1e-993e-1c3132161d6c@n58g2000hsf.googlegroups.com...[color=blue]
> My security center reports my Windows defender as turned off.However
> when i am trying to enable it by clicking "Turn on now" button,it
> prompts UAC and than nothing is changed. I have PC tools antivirus
> installed as a virus scanner.Does it affects the Windows defender?[/color]