Local disk(D:) seems to have replaced my (D:)

Hello,
Somehow local disk (D:) has replaced my normal samsung HD403LJ (D:) drive, and has autoplay on it also, in my computer all i had was the local disk(D:) showing so formatted it, then when i was trying to copy music back onto it from my external drive it said it couldn't write something and the whole (D:) drive is no longer showing in my computer. If i look in Device manager my samsung drive is showing there but i have no D drive showing in my computer, can anyone help at all i would be very grateful