DH and I bought our first home, which is 100 or so years old, last year. It has a partially boarded attic, and in the attic is a fairly big metal box addressed to someone in New York. It looks really old, old fashioned handwriting on the address label, super dusty like it's been there a long time.
We're not particularly "woo", but we've seen our fair share of horror movies, including those involving boxes in attics (Sinister, anyone?) and we weren't really keen to open it. Plus, I was 9 months pregnant when we moved in and we had other things to do, like build a million boxes of Ikea furniture.
Our friends (mostly) think we're mad for not opening it. One of them researched the name on the box and came up with an old newspaper clipping saying that the person died in an asylum from a religious furvour! Obviously it's probably a coincidence, but date wise it would fit with when the house was first built.
I must admit that my main reason for not wanting to open it is that it's dirty as fuck and i don't want to have to clean up all the mess involved in getting it down! My DH doesn't want to open it because he is actually scared of ghosts (has been known to scare himself while telling a made up ghost story 
).
The house doesn't feel haunted or anything like that, but it has a couple of weird quirks that freak us out a bit, e.g. the spare bedroom door (loft hatch is in this room) sticks for no obvious reason and you can get stuck in there. We've also both seen a shadow move under a door looking out into the hallway from the nursery.
So WWYD about the box? Open or leave it?