I am using Windows XP and facing 100% CPU usage since I installed Microsoft Security Essentials. I know that Windows Defender comes by default with Vista or Windows 7 but Iím not sure whether it is the part of Windows XP. Is it part of MSE or OneCare? Because whenever I ran MSE or OneCare I noticed that CPU usage goes upto 100% and it freezes my computer completely. Also when I start Task Manager I see MsMpEng.exe program running and it consumes the highest CPU resource. Can you guys suggest me something regarding this?