Your EndNote library becomes increasingly valuable to you as you add references to it. Consequently, it is imperative that you back up your libraries, along with any other important documents. Each library is made up of a file with the extension .ENL plus a corresponding .DATA folder. Always back up both the . ENL file and the .DATA folder.
Use the Save a Copy command or one of the Compressed Library commands to save a copy of your library to a removable disk (or elsewhere) for safekeeping. See Backing Up Your EndNote Files for more information about making backup copies of your files.