Just what IS Windows Defender?

[Jehu]

I don't even know what Windows Defender is for. I know that it starts slowing down my computer every afternoon and keeps the hard drives chugging away for hours.

It's driving me nuts! Is there a setting that will make it do its thing at night?

[Denis]

If you watch what you install on your computer and have a third-party virus/spyware software already, disable the Defender.

http://windowshelp.microsoft.com/Windows/en-us/help/31d797aa-091d-4d67-a556-dbfaf21bf0dc1033.mspx

[Reno Computer Repair]

Yes, there is settings to customize run time, and level of scan. A good program to add to the arsenal with Adaware, Spybot, A-Squared, Malwarebytes.