First thing to do is to remove any programs you aren't using. Go to the start menu to access the control panel. Then you can click "uninstall a program". Go through and anything that you no longer use, get rid of. (However, don't remove any programs that came with your device unless you understand what they are and are sure you do not need them.)
Next thing I would recommend is disk cleanup (control panel, administrative tools, free up disk space by deleting unnecessary files). That usually makes a big difference for me when I've used it.
The last trick I know is disk defragmentor. If you already have it set to run automatically (once a week usually) than this probably won't do much. If you don't have it set to run automatically, then I recommend changing that.
The other thing it could be is malware/viruses on your computer, but try the above first. There are free virus protection programs that you can get which can clear things up if you think viruses might be the culprit.
EDIT: Let me know how it goes.
Edited by JRHB14, 24 August 2014 - 06:40 PM.