Answer this if you are super smart?

i have been trying lots of new security software's to protect my laptop, sometimes it fells like that all i ever do. And i download any software which i find interesting. and now i have downloaded lots of stuff making my pc dull and slow. and some software's claim to be free but after downloading it, it says buy the new version for full protection its ridiculous. what i need is a free security software that can protect my pc the software must have most of the anti treatment in it[antiviruse, antispyware, antimalware, anti................. did i mention it should be free, thanks in advance