I have been using iTunes for goodness knows how long and as far as I am aware there are two methods.
The first is the "drag and drop" from your folder, which can take some time (as Beeker mentioned).
The other way is if you let iTunes look after the music. iTunes has a separate folder in My Documents which you can keep your music in instead, as this allows iTunes to "look after" your music. If you backup this folder, install iTunes and paste this folder into iTunes' default location, sometimes iTunes will pick up the folder and do it for you.
Of course, in your situation (as far as I am aware) you will have to use the drag and drop method, provided that the music you say you restored is the folder that you kept all your music files in.
Hope this helped.
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