[iTunes] OK, gimme a hand with this

[Devil Doll]

I think I need to delete a pref file for iTunes:

When I add artwork to an album, by dragging onto the artwork display corner
window, it seems to work. The artwork shows up in the corner.

But when I click onto something else and come back to the song in question,
there¹s no artwork. This seems to be happening with every song I try to add
artwork to. Which makes me think its an iTunes problem, not just specific
files.

Now if I trash my iTunes pref file:

com.apple.iTunes.plist

Do I need to worry about anything as far as losing ownership of my purchased
songs?