How do I delete a duplicate of my itunes music?

Before coming to the support site, I tried moving the library using my own methods which of course has back-fired.

My original library was on my Hard-drive C and I wanted to move it to Hard-drive D. So I went the copy and paste route which worked I have all the files in Hard Drive D but now I cannot get rid of the library on Hard-Drive C. So any suggestions how to fix this issue? thank you