You need to reinstall windows first off. I would think he has some kind of root kit installed on your machine or other malware that is allowing him to access your machine. If you change IP's or ISP's it won't help, the software that he has installed will just start reporting back to him you new IP.
The only way you will get rid of him is a clean fresh install.
You should also make sure when you rebuild that you have AV running and it is always up to date. Also might want to run some anti malware software such as adaware.
Let me know if you need any help.







OSCP - Offensive Security Certified Professional : Failed my first attempt at the OSCP exam




