Just to let you know that I have found totally free, faster and lighter antivirus for windows 7 i.e.. Panda Cloud Antivirus. Here is the link http://www.cloudantivirus.com/
Yes it is simple to install and use, but Panda is still in beta stage and adding features, and some issues (large or small) may remain. So for now I cannot give Panda Cloud Antivirus a full score, but its effective ability to find out malware makes it well worth.