RAR archive, 646 KB, for the ECS P21G motherboard at revision 3.0. A third revision suggests layout and parts may differ from earlier P21G boards, so confirm the marking on your PCB reads 3.0. The name does not state the contents; unpack it to see whether it holds a schematic or BIOS. Use such documents to follow voltage regulators, the power-on sequence and key signals, or to locate shorted parts. Any firmware dump should be written with a programmer only after saving the original chip contents.
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.