It's quite possible that you inadvertently downloaded MSE to your computer while visiting the Microsoft website; while MSE is not a virus of any sort, it will conflict with other anti-virus programs (such as McAfee).
MSE is easily removed going through your computers Add/Remove Program feature; if it is not the anti-virus program from Microsoft, then follow the steps laid out by Grif(M), for cleaning your computer of virus programs;profileBot#3290628