My music library has duplicated and some albums are combined, 2 or 3 in a folder. Tried to separate by dragging a group to empty folder. no folder would open. What to do

My music library, iTunes has duplicated, two albums of each. Also have many empty folders and some labeled "empty" were found to have 2 or 3 albums of music combined. I tried to move "a whole album" of 20 to 30 songs from one folder to an empty one by selecting and dragging, but no album would open. I have a desk iMac with version 10.6.8. I believe it is Mountain Lion added a few months ago, but everything was working allright until now. Don't know what to do. Afraid to import another album, but need the music.