I have a desktop and a laptop. Both running Windows 7 Ultimate (64-bit), and iTunes (latest version). I keep my music synced between the two machines using Windows Live Mesh, thereforee my libraries are always exact matches. That being said, lately I've been getting duplicate songs on my iPhone 4s. I've turned off "Music" syncing from iCloud by going to Settings > Store > Music (off). Not exactly sure that helped, but just did it just incase.. Anyways. I've used my iTunes to "Sync and Erase" all songs from my iPhone 4s. For some reason, the duplicates went away and now I just have 1 copy of every song. Why does Erase and Sync NOT erase and sync like it's suppose to? Why are there still songs on my iPhone 4s? I've had to go into my iPhone's filesystem manually and delete all iTunes stuff to get my songs to completely be gone from a fresh start... It's becoming annoying though.