on one computer?

no way

use only one anti virus..your computer will be much slower when you use two or more anti virus..i already tried it..

yes , i use because one virus scanner can detect virus but can not remove properly. other doing reverse of that action.And same time my virus scanner do not detect spy,trojenbut one thing is also true that having more than one anitivirus causes slow system performance in some extenti use McAfee and AVG

use one and try to keep it updated. if u have two os then use one in both. try to use McAFee