If you have a good anti-virus program and know you do not have a virus try these:
Enter UFEI or BIOS and set the RAM from XMP to the lowest setting and manually set the speed to 2133. Try a game if it plays well your RAM is the problem.
If, after that, games continue to be slow do the following:
1.) Check Task Manager for programs running.
2.) Do the following:
Download and install Spybot Anti-Beacon [it is free] and turn off everything except what you use, such as Bing [search engine] or Office 2015. In the Protection Tab, at the bottom of the page click Immunize. In the Optional tab click "Apply" buttons for everything you do not use.
This will auto "decrapify" Windows OS.
Every time Microsoft updates your OS check Spybot Anti-Beacon because sometimes programs are added or turned back on without Microsoft advising you.
You can also manually turn off what you do not want, however, that is a lengthy process, however, it works. Again, you will have to check to see if Microsoft turned something back on after you turned it off. As of the 2017 creators fall update Microsoft promised not to do that any longer, however, I continue to check because I do not trust them.
Do this for the Spring 2017 creators update:https://www.youtube.com/watch?v=--jlkMiRudw
Do this for the Fall 2107 crators update:https://www.youtube.com/watch?v=Xrsxy-eIN7Y