RAR archive of 920 KB for a P8H61-M LX desktop motherboard, a name following the ASUS P8 series pattern for Intel H61 chipset boards; the RG suffix likely marks a variant of the file set. The contents are not described in the name, so extract and check whether it holds a schematic, boardview or BIOS image. For firmware, back up the existing SPI flash with a programmer and make sure the dump size fits the chip. For drawings, confirm the board revision printed near the PCI slots matches before relying on it.
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 .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.