How to reinstall windows 7

Hi all,

Its been about 3 years or so since I got my laptop, and well things are starting to run kind of slow. Processor is hitting up to about 30% on idle, which isnt normal. I'm assuming I probably have a whole bunch of junk built up on it, and its probably a good idea for me to reinstall my OS. Question is, how? I have all my recovery disks and everything, but how would I uninstall my whole OS? And once that is done, do I just put the discs in? Or...