Clear your Windows cache files, this is your temporary file. It can grow up to a large volume and stop your computer from using RAM properly. In a sense slow it down by preventing it from using free space.Here is how:
Quit Internet Explorer, Firefox, or any other web browser
Click Start, click "Control Panel", and then double-click "Internet Options".
On the General tab, click "Delete Files" under Temporary Internet Files.
In the Delete Files dialog box, click to select the "Delete all offline content" check box , and then click OK.
Manage your startups. Your excess CPU usage is due to too many programs running in the background. You can cut these to bare bones by alter your ms config. Here is how:
Open your Start menu.
In the command screen type "ms config.exe"
In the "system configuration utility",click either "service" or "start up" tab
Unchecked all programs that your are no longer using.
now check your speed using