First is it to always clean out all the junk that is left behind by the operating system and the browsers. You can easily do this using the Disk Cleanup utility included on the windows systems. You can clean up the registry. However, you should be very careful with the registry. Any wrong move might mess up everything
Search and destroy viruses and malware on your PC by installing an anti-virus security program and setting up an automated maintenance schedule.
Defragment main and partitioned drives to keep your computer running smoothly.
Uninstall software programs and personal files like pictures, movies and music that are no longer in use to free up more space. The more the space, the faster the PC will go. You can also run the msconfig command in the RUN command prompt to uncheck start up programs that you do not use