Mac Problems

I have a pre 2013 build that is now running very slow and freezes up all the time. It doesn't matter whether I am online, in email or any other apps the problem is persistent. I've run the Apple Hardware Test which is used for pre 2013 models. No problems were found. I've run MacKeeper with no apparent change to the problem. I've run MacScan, no change.
I am running OS X Yosemite 10.10.2. I did notice that the Mac became slower once I downloaded Yosemite.
I've copied all of the support tutorials from the Apple website. I've tried as much as I can from the instructions given by Apple. No changes to the problem.
Does anyone know how to attack the problem aforementioned?
I get no error messages.

 

You should uninstall Mackeeper as it is not the best app to diagnose your Mac. It will bring more troubles for you. Is your Mac HDD fine? Please run Disk Utility << Verify and check your drive. Also try to take latest backup of your Mac OS X.