Ghosts at Hogwarts

[thekrenz]

No: HPFGUIDX 99799

As I was reading the posts regarding the possible graveyard at 
Hogwarts I saw a reference to Sir Nick's song on JKR's website.  I 
reviewed his song, and a thought occured to me.  Were the ghosts 
wizards when they lived?  Surely Sir Nick was because he was executed 
for attempting to fix someone's teeth.  And by the same token, were 
the people who arrested and imprisoned Sir Nick wizards?  I do hope 
JKR will give us a little more background on the transparent 
residents of Hogwarts.
Just a random thought. Any comments?
Cyndi