How do I prevent intruder into my pc

I have a pc, yet currently it is being used by a intruder remotely. that intruder basically has my ip etc… to gain access to my computer.

whenever I go on internet, that guy will detect me and use my pc to browse his webpages.

how do I stophim. and prevent any intruder access.

I have install a intruder alarm, a personal firewall, etc… that guy is still able to intrude my pc. I wanna to catch him red handed
is there any software that I can use????