Need Some Help from Gurus!

So long story short, my self-entitled teenage son decided it'd be a hoot to look at porn and post inappropriate content on his FB page so I took his computer away forever. I am selling it! Yes, I know, drastic but necessary imo. Now I can't get on his computer to reformat it to get rid of it. I'd smash it with a sledge hammer but I decent amount of money for it and would like to recoup my $ somewhat. I don't know what to do to get around his password! Any help for me? Is there someplace I can take it without paying a fortune to have someone else do it? I have receipt for it still as I just bought it two months ago.

In a perfect world, that would actually work but he there are problems beyond what grounding can do. We're beyond stripping his room clean sans a mattress to sleep on and only the minimal amount of clothes to last a week. He'd be in a juvenile home if the system worked the way it should. Ugh! He won't voluntarily give me the password.

I don't have a CD. It came with W7 installed already. No disc.

Okay, remember I'm a low-tech Mom but I do know that I have to boot from the CD but the computer is not set to boot from the cd. How do I change that? It keeps taking me to the log in screen.

Compaq Presario CQ56.
Okay I know not an expensive laptop but for our family it is.