Easy Fixes for Slow Computers: 2. Run an adequate anti-malware program (and keep it running).
Malware on your computer could install and launch processes that bog down your computer and cause the speed issues that make you nuts. And malware is sneaky; you may not even notice that it’s there.
It’s critical to use the right software to detect malware, clean it out, and prevent future infestations. I suggest AVG (although truth be told that company is starting to get on my nerves). Their free anti-malware program is very good and will not cause further problems to your system (like Norton, which I hate).
It’s up to you, but you really do not need to spend any money on anti-malware. The AVG version is completely free and suitable for home computers.