You haven't fixed the problem though, you fixed a symptom. Go into iTunes Preferences and check where your iTunes media folder is.
Your description isn't very clear. You said you "can't download any music". Well, that wouldn't have anything to do with iTunes, would it? Did you actually mean you _can't download music_, or did you mean _you can't add music to your iTunes library after it is downloaded_?
And what do you mean by "download"? Music purchased from the iTunes Store? Music purchased from Amazon? Music downloaded from illegal sources?