Vista and 7, may apply to others.
I have been much puzzled by windows PCs seeming to slow down gradually over time. I tried various things, CCleaner for example, but nothing really helped. Then one day I set up an extra user account so that a friend could use my PC. When logged on as the new user the machine was as-new fast again.
I therefore created a new user account for myself and moved all of my files over. Job done. Machine fast again. I have repeated the process on one or two other occasions on different computers with the same result.
One thing is that if you have any applications installed for "This user only" then you might have more work to do. I just left the old account on the machine in case I ever needed to use it. I never have.
It is very easy to try out, just create an account and log in. Log out of the old one of course, don't mess aroung with user switching. I recommend a reboot I suppose.
Please post any results.
Also:-
After being plagued by the fan running nearly constantly along with high CPU I turned off automatic updates. That stopped the fan running almost entirely. I didn't have actual performance problems since it is a fairly fancy PC for its time (2 cores x 2 hyperthreaded so total of 4 virtual cores) but the fan and heat were annoying.
Good luck.
Last edited by jimjim1; 4th Feb 2017 at 17:51.
Reason: added heat"