Did you restore using Time Machine? If not you can tell iTunes to import to its library and you point to the drive and directory where the songs are... this will restore your songs but not your play lists.....
If you made a good backup of your iTunes folder then you could just copy that folder to the iTunes music folder... that might save your playlists..
The primo way to restore would have been Time Machine... I just used it to restore my Mail program... it worked great...