Zip package of 627 KB for the P5KPL-CM, an ASUS LGA775 desktop board from the P5KPL family. The name lists no revision or document type, so check the contents once extracted. At this size it most likely contains a BIOS image for reprogramming the flash chip with an external programmer. Do not confuse it with the VM or AM variants, which are different boards needing their own firmware. Read and keep the existing chip contents before writing, and verify that the image fits the installed flash.
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 @laptopchiplevelrepair. Enginerys does not host this file.
How to open a .zip file
Compressed archive that every operating system opens without extra software.