RAR archive for the Sony VAIO VGN-AR series, tied to motherboard MBX-156 and design code MS20. The exact contents are not stated, but the package most likely contains the service schematic. Unpack it with 7-Zip or WinRAR. Such documents help in diagnosing no-power and no-video faults by following rails from the adapter input through the charger and system regulators. Since VGN-AR units may use different boards, confirm the MBX number on the PCB matches before relying on part values or pinouts.
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 @alischematics. 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.