If your computer is running slow so maybe any kind of virus has reached in your computer.
You can cleanup your computer.
You can remove temp files of your computer.
You can run clean mgr in your computer.
You can remove all unwanted software from your computer which you have downloaded.
You should put anti virus in your computer and scan your computer by anti virus once in a month.
You have to up to date your anti virus .
You can clean dust also from your computer by blower.