CCleaner is a freeware system optimization and privacy tool. It removes unused files from your system – allowing Windows to run faster and freeing up valuable hard disk space. It also cleans traces of your online activities such as your Internet history. CCleaner also fixes your registry. But the best part is that it’s fast (normally taking less than a second to run) and contains NO Spyware or Adware.

Advanced WindowsCare Personal is a comprehensive PC care utility that takes a one-click approach to help protect, repair, and optimize your computer.

Other free registry cleaners available include Eusing Free Registry Cleaner, Registry Distiller and TweakNow RegCleaner Standard.

Below can help you speed up your pc:

For IE, click Tools, Internet Options delete files (offline files) clear history (set days to save to 0 if you want) click o.k., and Restart

For Firfox, press ctrl+shift+del, and click clean private data.

Manage your startup:
Open your Start menu -> Click Run -> In the command screen type "msconfig.exe" -> In the "system configuration utility", click either "service" or "startup" tab -> Uncheck all programs that your are no longer using.

De-Fragmenting
1. Right click of C Disk.
2. Click properties.
3. Click tools tab.
4. Click "Defragment now".
5. Click Defragment.

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.

Learn "Why Is My Computer Running so Slow?" and "How to Speed it UP":
http://downloadlk.com/WhyIsMyComputerSlow.htm
Use the tool: http://downloadlk.com/themosteffectiveregistrycleaner.htm