Here are some ideas, get "key scrambler pro", this program scrambles every thing you type so anybody looking in will only see random numbers and letters. You can get Key Scrambler personal for free but it only scrambles all your internet login information, Key scrambler pro scrambles every key you type, good key encryption. You could also get a program called "System Tuneup" this program not only fixes all errors in your system but it deletes all your internet browser history and search and deletes internet cookies, and .dat files it will wipe everything clean and securely delete it to the point that it cant be recovered by others. There are a whole bunch of other files it will do it to also that you don't need, it even sped up my computer. You can go to there site and download it and have I think it's a 30 day free trial, Im using it now and have no problems with it. You could also look into a program to surf totally anonymously, Maybe check out "hide-my-ip.com" I only say this in the intrest of protecting your privacy from hackers and such. I don't aprove of any illegal activity.
Now of course this will not help with your current situation as they already have a list of what you have been into. To be honest with you to though I don't think alot of these internet service providers are willing to give up there customers for a lot of different things unless they are severe enough, after all they just loose money if they do.
Again though, just don't do anything illegal and you will be fine anyway, the programs above though should offer really good protection from hackers though.
I also like Spybot Search and Destroy, Ad Aware SE, I have computer associates antivirus, popup blocker, and spyware protection. I think im going to purchase the computer associates firewall to, this way i get a better firewall than windows and I know nothing will conflict. I used to like Zone Alarm Firewall but I can use it with computer associates and computer associate protection I get free with my isp.