"at the moment im using "microsoft security essentials" with windows firewall,"
Very sensible - stick with it.
You might want to add the free version of MalwareBytes antimalware, which you can use for an occasional scan and in the event that a nasty does get through.
http://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html?part=dl-10804572&subj=dl&tag=button
If you decide to install it, you will be asked if you want to install a trial of the Pro version. Make sure that you say No, and install only the free version.