Small ZIP archive of about 242 KB named only H61M-C, which matches an Intel H61 chipset motherboard model name but gives no maker, revision or content type. Several vendors used similar H61M names, so check the board silkscreen and the files inside before relying on them. If it holds a BIOS image, write it with an SPI programmer only after reading out the original chip, and confirm the image size fits the flash. If it is documentation, match the board number and revision first.
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 @schematicslaptop. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.