RAR archive for the ECS B25H4-AM motherboard, revision 1.0, weighing 1.81 MB. The name gives no content type, but ECS board packages of this kind usually hold a schematic in PDF form, sometimes with a boardview or BIOS image. Extract it with WinRAR or 7-Zip and check what is inside before planning a repair. Confirm that the model and revision silkscreened on the PCB match REV 1.0, because power circuits and component placement can change between revisions of the same ECS desktop board.
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.