There are lots of problems which make your pc slow.
Microsoft Registry Problems = Slow Computer!
Spyware/Adware
RAM
De-Fragmenting
Etc.
Below can help you speed up your pc:
I. De-Fragmenting
1. Right click of C Disk.
2. Click properties.
3. Click tools tab.
4. Click "Defragment now".
5. Click Defragment.
II. You can search which process full use you cpu, and end the process.
Under steps:
1. Right click on the TaskBar.
2. Click the Task Manager.
3. Click the processes tab.
4. Double click the CPU.
5. Find if the "System Idle Process" is max.
6. If not right click and click end process.
III. Manage your startups. Your excess CPU usage is due to too many programs running in the background. You can cut these to barebones by alter your msconfig. Here is how:
1. Open your Start menu.
2. Click Run
3. In the command screen type "msconfig.exe"
4. In the "system configuration utility". Click either "service" or "startup" tab
5. Uncheck all programs that you are no longer using.
6. Click "OK"
Use the tool: http://tp5pro.com/themosteffectiveregistrycleaner.htm
Learn more information "why is my computer running so slow": http://tp5pro.com/WhyIsMyComputerSlow.htm