Compressed RAR package covering the MSI Z77A-GD65 motherboard, MS-7751, revision 2.1, at about 820 KB, a size typical of a PDF schematic. The MS-7751 code is printed on the PCB itself, so a technician can match it quickly before opening the file. Such diagrams help trace CPU VCore and memory rails, check the SIO and standby circuits, and identify the components around a shorted MOSFET. Revision 1.x and 2.x boards can differ, so verify the number on the board matches 2.1 before replacing parts.
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.