Norton does not find adaware/spyware, which probably got installed when you downloaded your new skin. Believe it or not, Microsoft AntiSpyware is pretty good (because Microsoft didn't create it). I would download it, update the defs and run a full system scan. Just be careful when removing, because it will even identify some valid programs as spyware (such as VNC) because they do pose security risks.
http://www.microsoft.com/athome/secu...e/default.mspx