Computers are just like cars in the sense that they need regular maintenance. Set aside an hour or two a week to clean up your computer of temporary internet files, history, cache and cookies. I use CCleaner for this. The program can be found all over the internet. Just by running this software once a week you can dramatically increase the speed and overall performance of your system.
CCleaner Download
Another thing to consider is avoid cramming your system with programs you don't use, and data you probably don't care to have. Perform your house cleaning. I run through my system deleting old files, folders and even emails I no longer need to have. Once a month I go through my installed Programs and remove any that I no longer need nor want.
Last thing I wanted to mention to speed up your PC is start-up programs. Start-up programs are programs installed and configured to launch themselves in the background when turning your PC on. For the most part all of these can be remove but please use your best judgment. Anti-virus programs will be configured to start-up with your computer as well so be careful not to remove any of their components.
To do this - Click start, then click Run and type msconfig
This will launch the Microsoft System Configuration Utility
Click the Start-up tab and remove what isn't needed
Thanks for reading. Hope this helps!