Recently I have noticed after rebooting my computer msmpeng.exe will run using over 90% of the processor. This will continue for several minutes and I'm not able to do anything. Research shows that this is related to Defender, but I'm running MS Security Essentials and Defender is not installed on my PC. Is it related to Security Essentials and is it anything I need to be concerned about. I also ready that it could be a well disguised virus, but I ran several virus scans and they all came up clean. Thank you for your help.