ECS 915G-M3 motherboard archive, revision 1.0, stored as a 1.16 MB RAR. The model indicates an Intel 915G chipset board, while the name does not state whether it holds a schematic, boardview or BIOS image. Extract it with 7-Zip or WinRAR to confirm. Another, smaller package for the same model and revision exists, so the two may contain different material, and comparing them can be worthwhile. Check the PCB revision first, then use the diagrams to follow power rails, the CPU VRM and reset signals.
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.