A few Questions About Ghosts

[coastertch]

No: HPFGUIDX 41974

Hello everyone, I'm new here. I'd like to ask a few questions about 
ghosts in the Potterverse.

I'm guessing that there ARE muggle ghosts around (the old man in GoF 
who comes out of Voldemort's wand), but do they know about wizard 
ghosts? Do muggle ghosts and wizard ghosts associate with each other?

Is the Headless Hunt only for wizard ghosts?

Do wizard ghosts still have any of their powers?

And finally, we don't know yet why some wizards become ghosts and 
other don't, but do you think it's any different than the reason 
muggles become ghosts?

Thanks for the help.

Tyler