Notes about the LDR file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries
, unused processes and other unfavourable system settings to identify slowdown issues.
The LDR file type is primarily associated with 'LDraw' by Estate of James Jessiman. LDraw is an open standard for LEGO CAD programs that allow the user to create virtual LEGO models and scenes. The Wikipedia link has a discussion of viewers and converters.