When you create a library, EndNote assigns the “.enl” file extension to the file name (e.g., My EndNote Library.enl) and creates a corresponding folder (e.g., My EndNote Library.DATA). [Note: The .enl extension is visible if you check the file’s Properties.) Both the library file and .DATA folder should be stored together in the same location.
I’m not clear as to where the problematic library is located as your initial message mentioned the USB hard drive but your recent message seems to identify the EndNote folder within “Programs” on your hard drive. BTW, you didn’t mention your computer’s operating systemb but if you’re using Windows Vista or later, the EndNote library file and .DATA folder should be moved to the Documents section of your computer.
Otherwise, the key issue is to locate your EndNote library file and remove the Read-only attribute and recheck the file to confirm its removal. If you encounter difficulties in removing the read-only and your file happens to be in the Program Files section of the hard drive, you can try copying the file to the desktop, remove the read-only, then copy the file back to the Programs Files.