If I ever feel that a PC is running slow, I completely re-do it from scratch. I'll DBAN the whole thing, then install the OS, etc. etc. You won't believe how much faster your computer will be. Probably a bit faster than when you first received it from the manufacturer since it will be void of bloatware...
Here are the DBAN instructions:
https://www.it.cornell.edu/security/...tices/dban.cfm