Can I reboot my laptop to wipe off everything myself?

I bought a Dell inspirion laptop about two years ago. It is so slow, and windows frequently stops responding becuase it is so slow. I really want to save my important things on a memory stick/disc and just reboot my laptop so it is like new again. My friend told me I have to pay around $150 for a computer store to do it but I also heard I can do it myself. Can you please lead me through this process if i can reboot my computer myself?