How to excise a hacker and keep him out?

My pc has been riddled with nonsense and have used every resource that I know of (that is, what has been told to me). My health is becoming more of a challenge and having to deal with all the trash of his maneuvers on my pc. My ability to function in this world is growing slimmer by the day. The pc is my only link to the outside world on a daily basis. I live a very reclusive lifestyle and don't want to have this person controlling my pc. It's an outrage that someone can take over control of so many vulnerabilities. Any istance is appreciated.