RAR archive for the ECS 915G(P)-M3 desktop motherboard, revision 1.0, 860 KB in size. The name does not list the contents, though archives labelled this way for ECS boards usually hold a schematic in PDF form. The 915G(P) designation suggests a board offered in 915G and 915P variants, so confirm which one you have. Before tracing power rails, VRM phases or a shorted line, check that the model and revision silkscreened on the PCB match revision 1.0, since ECS changed layouts between revisions.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @IT_SERVICE_WORLD. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.