2 Answers

You will also need to look at your MSCONFIG-Startup--  I won't explain how you get to this because if I need to do that, you don't belong there..You may have many programs running in the background (tsr) that you don't really need, and of course, you could have a virus or Trojan eating up your resources, you could be on an old computer with limited CPU and memory-- There's many reasons why a computer is slow.. if you don't have computer knowledge to check for these things then take it to a qualified service center.. 

First try downloading all un needed items that you want to save onto a disc or stick.  Delete all others and empty your trash bin.  Delete all cookies.  disc clean,  and defrag.