The Benefits of a Clean Installation
What is a clean installation? And what are the benefits?
A clean installation is when you erase all existent files and reinstall the whole system. This way, you get rid of the junk in your hard drive and also eliminate some hidden programs that could be slowing your computer. If you need to keep your files, you can back up them. After the clean installation, only the essential applications are on your computer, which will be working faster and safer. You can reinstall additional applications as you need them. Make sure to have the registration keys for purchased apps. I recommend a clean installation if your computer is crashing or very slow.
If you want to know more about it, here is an excellent article to read on Lifehacker: In Defense of the Clean Install.