help? someone.please?

I got my computer back with a new hard drive (again) and a new system board (again too). I transferred everything that was on my external hard drive back onto the laptop. Unfortunately, i realized too late that when i saved data onto the external drive, it was saving a whole new copy- i didn't specify it to copy over duplicate files. So now i have 40.3G of music in iTunes- about 4 times as much as I really have. I'm not sure the best way to delete three of the four copies of each song. I certainly don't want to do it manually. I'll be working on it forever. What i really need is my own personal tech support person to show up and help me organize all my electronic data. For someone who's so anal about organization in the real world, i'm horrified at how disorganized my life is in the virtual world.