No antivirus is installing,xp total security showing is showing infection,no pc suite working in my laptop?

1 day when i connected my sd card to my pc(which do not contain antivirus) .the viruses in my sd card spread all in my laptop.its about 4-5 months ago.till now i tried everything including pc tool,spyware doctor,avg nothing works and when i tried to install antivirus it shows NSIS error.i am frustrated what to do with my laptop.plz help someone ,eagerly waiting for your answer