ITunes Music Transfer?

ITunes/iPod music transfer help!?

• Basically, my computer had Windows Vista and I wanted Windows 7 so I reformated it, and I transferred all my music to my external hard drive (there were 500 MP3.files). After my computer was reformatted, with Windows 7 I transferred all 500 music files to my computer, all 500 play fine on Windows Media Player, but when I transfer them to iTunes, they don't transfer, only about 300 do. That's my problem. All 500 music files worked fine on both iTunes and Windows Media Player, before the computer was formatted. Now all 500 only work fine with Windows Media Player, and about 300 with iTunes. When I try and transfer over one file it comes up as the ' + add ' in iTunes, but it doesn't transfer over. Does anybody know what is wrong, or what I can possibly do to try and make it work? NOTE: All my music has been downloaded externally, and through CD's, not by using iTunes! Thanks, and sorry for the lentgh of this :/

• Answer:

  What You Have To Do, is Open Your External Source(hard Drive) and Select Your Music Files--> Drag To iTunes Library.