Check your running processes and look for any process that is using huge amount of CPU or memory, and looks unfamiliar. Do a Google search on that process and see if you can find anything. If you find that it is bad, try to find it in your system and remove it. If you can't find any info on it, remove it too, unless it is used for some custom programs that you might be running.

Clear your Temp internet files, cookies, and registry values for such process.
This will solve your problem
Good Luck.!!
And,,,, stop going to porn sites...