Advice on wiping hard drive with bootcamp installed

[Dukey]

Hey there,

So I'm selling my old MBP (late 2009, 2.8 GHZ intel core 2 duo) to my cousin and I was wondering what is the best way to go about clearing out the system.
I also have Bootcamp installed in it as well so I'm questionable about wiping the whole drive.

I was wondering what was the best way to go about cleaning 99% of the my photos, video, music, apps, etc. and keeping boot camp still installed. Thanks