Help with moving music to new computer

I have run into a problem while following the iTunes: How to move your music to a new computer support artical. I believe I followed the instructions using my iPod as an external hard drive but when I finally went back to iTunes, the songs are listed, but they do not open. Instead, I get a pop up that says, "The song "xyz" could not be used because the original file could not be found. Would you like to locate it?" This is the case for about 500 songs that were previously on my old computer in iTunes

I have a new window's 8 computer and had just downloaded iTunes onto it. I was so worried about losing my songs that I specifically looked for help on how to seamlessly accomplish this.

Any help would be greatly appreciated! Thank you