Gigabyte GA-G31M-S2C motherboard materials packed into a 1.14 MB zip archive. The S2C is a micro-ATX board on the Intel G31 chipset by its model designation; the file name says nothing about revision or exact contents. Similar sized Gigabyte packages usually carry a PDF schematic, which lets a technician trace the standby and main rails, check the CPU core regulator, the DDR2 supply and the reset logic. Match the revision printed on the PCB, often written as REV followed by a number, against the document before trusting component designators or values.
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 @cyberlanelectonik. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.