That little box, of course, means that that particular symbol is not in the current font that iTunes is using. Not sure what happened there, but as you did a reinstall of Windows, I would guess that maybe, somehow, somewhere, that particular font did not get the word that it needed to reapply itself. I can't for the life of me remember what the default font for iTunes is. It gets mentioned around here every now and again (often in the OS X area for iTunes), but right now I'm at a loss.
What happens if you have iTunes re-run it's installer without uninstalling it? Choose the repair option and see if that doesn't put the needed font in there for you. Of course...it's possible you told Windows not to put it back in. Maybe check that the ever popular "wingdings" is installed. Don't have my PC available right now, but on my iBook it's in with the symbols that are similar to that set.
