Format your HDD, Reinstall your operating system (Make sure your computer/user name are different)

Make sure your IP isn't set to static by your ISP (This'll be in router settings, you want it set to dynamic)

I recommend checking your IP address before hand (Google will show you hand) then turn your router off for between 1-12 hours. (The longer it's off, the more likely your old IP address will get taken and you will get a new similiar one)

Congratulations, you're now a new person. Don't get caught again

--Edit--

Derp, just ran through the comments before and it seems although they're pointing to this.