Question about Norton or Windows 7?

I hope someone will understand my question. My first computer (I bought it in 2003 and it came with Microsoft Windows and a lot of other nice programs,) died an ungraceful death last week. I bought a new tower (and printer because it was dead also) and the tower came loaded with Windows 7. I immediately re-installed Norton, which I did before any surfing.

I am astounded at the difference between this computer and my old one - and know that sooner or later I will figure out how everything works... but I do have one question: When I run my Norton quick scans, (and full scans) they are way faster than the old computer, but they are picking up a heck of a lot more security risks (so far just tracking cookies) than they were before. This is a good thing, I know, but why so many? I have the same Norton subscription, only the computer has changed. What is making the difference? Norton is the only security system installed now - my computer store distinctly said that if you install Norton and McAfee, that they can fight and cancel each other out.

I am happy my computer and everything seem to be working and safe, but I do have to wonder why!