Hi Ehre, Before you start removal,  open the McAfee Control Center, and DISABLE  all of McAfee’s components that you see enabled and running. Next, as Joe mentioned, via the Control Panel, locate the section to uninstall programs, and use this to UNinstall McAfee.  Following that reboot. Confirm that Windows Defender is now running as your anti-virus. If Defender is running, all is well. You're done. If not, run the removal tool, MCPR.exe, and reboot. (I no longer recommend that users run the McAfee removal tool immediately following the uninstall because some folks have recently had a problem with it.)  
Hi all,  I recently bought an XPS 8500 with windows 8.  It came with a garbage trial version of Macaffee virus protection.  Windows 8 comes pre-installed with Windows Defender.  However you can't have both.  The Macaffee trial subscription recently expired, however it is not readily apparent how one removes macaffee or activates Windows Defender.  Each time I get to what seems like a relevant window, it only says Windows Defender cannot be used simultaneously with Macaffee, but there is no apparent way to switch from Macaffee to Windows Defender.  Please help.
Activate Windows Defender