I've moved all of my MP3s to a new location. iTunes appears to still be looking in the old location because it displays no artwork and an exclamation next to each song.
Is there a way to tell it "it's all over here now"?
What I would do is select all of the stuff in the library and delete them out of iTunes. Then go to where ur music is located and drag them back over.
iTunes stores the path to the music files in a library file, so moving the files without using iTunes is a bad idea (see this article for detailed explanations).
But there is hope! I transfered my own library from Windows to Mac by editing the iTunesLibrary.xml. The location of all files is stored in that file. There you have to replace the old folder path with the path to your new location. The procedure is detailed here
If you are comfortable with iTunes managing your files you can also move the files back to the old location and then let iTunes perform the move.