There is only one file type that uses the .PD5 extension:
Windows Live Photo Gallery Information File
Database file created by Windows Live Photo Gallery, a program used for managing home photos and movies; stores metadata about personal images and videos; used to track information on personal media files.
By default, PD5 files have the name Pictures.pd5 and are found in the following user directory:
%USERPROFILE%\AppData\Local\Microsoft\Windows Live Photo Gallery
If a PD5 file becomes corrupted, it may be renamed to OLD_Pictures.pd5, and Windows Live Photo Gallery will automatically create a new Pictures.pd5 file.
NOTE: Microsoft Windows Live Photo Gallery is no longer developed.
Updated: August 27, 2020