A question about ghosts in HP world

[Rachel Bray]

It was once discussed why some people become ghosts and 
some don't.  I don't remember the discussion.  Could 
someone please remind me why some people turn to ghosts and 
why some don't.  We're (office folk) discussing why Harry 
won't see his parents as ghosts and I can't remember why 
that is.

Thanks.

Rachel Bray
- who would never be offended or disgusted at any 
introduction to a new slang term whether it be American, 
British or other...Thank God.