If it is a melon, in most cases you don't. except for pickling and preserving melons they are eaten raw. Cant tell from the photo what this may be. While it looks like a watermelon, there are squash with similar shape and markings. If your neighbor is into oriental crops, possibly a gourd.

It's a wintermelon. You can cook it by stir frying it, or boiling it as part of a soup.

If it is the wintermelon/Wax gourd (Benincasa hispida) it will have firm white flesh. Most used in soups. Recipes http://www.google.com/search?q=wax+gourd&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=fUJvUNKKEMXs0gHK9IBw&ved=0CC4QsAQ&biw=1440&bih=785#hl=en&tbm=isch&sa=1&q=wax+gourd+recipes&oq=wax+gourd+recipes&gs_l=img.3..0i24.134926.137740.0.142001.8.3.0.5.5.0.142.374.0j3.3.0...0.0...1c.1.dGZ7fZtxT_4&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&fp=789d08312cda32c5&biw=1440&bih=785

Here is a link that might be useful: Wax Gourd