My CPU usage goes to 100% usage

Hi Dorothy,
Hope the following steps will guide you in fixing of this issue.
Mostly, that is immaterial.
If it is truly retardation plume, it is likely you don't have enough RAM, or loud module, as in MB’s as 256 or 512 then add some more RAM, or slower HDD, a store anomalousness, lacking VGA, a weakness set cross, many another component troubles or too more software programs running behind. Suggest you run “Hijacker” software to see how many programs are running behind.
If dozens of programs are loaded and all are running then it would be sufficient to effort the job you exposit.
If you have installed program like Norton Antivirus, uninstall it and install Microsoft Security Essential only and see how some modify you get.