Removing duplicate songs

So I want to back up my iTunes library to a flash drive, and have been told the best way to do this is to copy the entire iTunes folder and paste it onto the drive. This wouldn't be a problem, as my music is 6gb in iTunes, and the drive is 8gb, except that then I found out my iTunes folder is 20gb.

After a bit of investigation I found out that for most of my library, each song has 2-3 copies.

Obviously I could go through thousands of folders and delete each copy one by one (except in this case, I'm not sure which is a copy and which is the original that links back to my iTunes), but that is a bit unrealistic and I have nowhere near the patience to do it.

Is there any easy way to delete all the duplicates in my music folder? (No, I'm not talking about going into iTunes and clicking display duplicates.)

edit: figured it out, I had to sort the folder by song instead of by artist (sorting by artist put every song as music>itunes>artist>album>song, which takes a lot longer to get to than simply music>itunes), then I could set it by date added and delete them all at once.