im an at&t customer and i get to download mcafee internet security suite for free. i’m just wondering if windows defender is needed in this case since i know that running 2 antivirus softwares will causes conflicts between the programs and slow the computer down.


Well this is true that running two antivirus softwares slows pc down but that depends upon the configuration of your hardware too. but in your case when you have installed an internet security already you need not to run defender.
Windows Defender is just an antispyware program so there shouldn’t be a problem in keeping it. However, if your antivirus is Microsoft Security Essentials, Windows defender will be automatically be disabled to avoid any conflict with MSE.