1. Clean up your disk by removing unnecessary files and programs.
2. Disable any unnecessary startup programs.
3. Update your operating system, software and drivers.
4. Run a disk defragmenter to optimize file position on hard drive.
5. Remove malicious software and viruses.
6. Add more RAM if possible.
7. Use a reliable registry cleaner to clean your registry.
8. Keep your PC cool by ensuring it has adequate airflow.
9. Use a HD cleaning tool to remove outdated junk files.
10. Run a thorough anti-virus scan of your system.