First things first. Try a simple system restore (START > ALL PROGRAMS > ACCESSORIES > SYSTEM TOOLS > System Restore) back to yesterday or before you go this problem. This often solves the problem.

Next, remove Norton. It's honestly fucking shit, never does what you need it to, and slows the PC down as it's a complete resource whore. Bin it and download AVG Free from Grisoft - http://free.avg.com/ww.download-avg-...s-free-edition

Run a scan with that, quarantine and remove everything it finds.

Next, install and scan with Ad Aware from Lavasoft - http://lavasoft.com/products/ad_aware_free.php

Next, install and scan with Spybot - http://www.safer-networking.org/en/download/index.html

All the above programs are open source freeware and as such are free. And they all work!