Probably a good idea to start over with a reinstall. If you're having problems, might even want to consider Dbanning your drive (http://en.wikipedia.org/wiki/Darik%27s_Boot_and_Nuke
Have you ever considered using Linux?
We have a laptop we use just for internet access and it has Windows OS plus Norton, BUT, for the past year, we've been using Linux. The Linux OS is on a thumb drive and we boot to it whenever we want to go online.
The nice thing about running the Linux off a thumb is that you never have to use your computer's hard drive (where all those cookies, virus and malware require access to), so when you shut down your computer, nothing is left behind to attack you. Any screen shots or cut&paste docs I want to keep from a surf session I dl onto another thumb and transfer to one of our other computers. I store nothing of value on the internet computer's HD, so nothing is ever at risk.
If you don't have desire for 2d computer dedicated to internet, then if you have a laptop, you can accomplish the same thing by getting a spare hard drive (and caddy). Then, slide in one HD when you want to go online, and slide in the other when you want to store information that is personal and you don't want exposed to hacking.