Still wondering about ghosts

[Miss Tery]

No: HPFGUIDX 75101

I once read an interview with JKR, one of the questions was why some 
wizards become ghosts and some don't. She smiled and answered that in 
book 5 the answer to that question would become clearer. Well now 
I've read the Order of the Phoenix and I think I was just as 
disappointed as Harry Potter about the explanation that Nearly 
Headless Nick gave, because although he is dead, he doesn't know a 
thing. Have you got any ideas about this subject?

Miss Tery