I remember this happened to a girl that I knew, when you click on any song in iTunes it stays at 0.00...... its most likely that your soundcard driver has been corrupted.
A simple test (which I did with hers) is to make a new account in windows and install iTunes on it and put some songs on..... if it works there (which it did when I did it) then you have to go back into your normal account and reinstall your soundcard drivers.
Sometimes other programs which use the soundcard which may be causing conflict... this is why it can corrupt. A new account has no other stuff on it so its a great place for testing.
Robin