Small 285 KB RAR archive labelled M5A99X_EVO, a name matching an ASUS AM3+ desktop motherboard, though the brand is not stated in the name and the contents are not described. Its size suggests firmware or boardview data rather than a full schematic set. Open it to check what it holds. If it is a BIOS image, back up the existing chip before reflashing with a programmer. If it is board data, use it to trace rails and locate 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 @boardview. 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.
7-ZipWinRARThe Unarchiver (macOS)