This guide will give you tips and ideas on how to make your PC faster. The advice applies to all operating systems and is not intended to be an in depth guide!
This in itself will not make your computer faster, but the less files on your computer, the less the antivirus has to scan. You also reduce the chance of an old application being a security vulnerability.
If you have a lot of applications that run when your computer starts (e.g. Quicktime, camera software), see if you can disable the ones you don't need. This is usually found in the applications setting. For most people, security software should be the only application that runs when the computer starts.
Are there other smaller, less resource hungry applications that are better than what you are using?
Over time, the files on your pc may become fragmented. This can slow down the loading of applications and files. Running a defragmentation tool will help fix this.
Viruses and other bad program can slow your PC down, make sure you read this guide to Securing Your PC.
Not a speed up tip, but keeping your documents and pictures organised into sensibly named folders will enable you to find them faster and work more efficiently!