Greetings usamrf,
The .enlp file extension is indicative of an EndNote library saved in the package format. The .enlp file contains your library’s .enl file and associated .Data folder. This library type is Mac-specific, so you’d want to avoid this option if you use a Windows version of EndNote on another workstation or plan to share your library with any colleagues using EndNote on Windows. Saving your EndNote library in the package format adds an extra step to the Recover Library process - you’d have to move the underlying .enl file and associated .Data folder out of the .enlp package file prior to choosing your .enl file for recovery purposes.
Please let me know if this helps.