Since when has Norton been free (except on trial)and Ewido unless you are careful will remove bits of legit programmes and stop them from working.
All you need are Adaware from Lavasoft, A squared free edition from emsi software, Spywareblaster from Javacool software (watch out for malicious copies from other sources) and Spybot Search and Destroy from Safer Networking
These will prevent or remove just about anything and can be trusted