Newtus, do you have a Mac? It seems that Mac computers name any file type they don't know the file type of "unix executable file". It's possible to rename the file to give it a file type but I'm not sure what you'd use. Maybe some picture format like jpg or gif? Make sure you have a backup copy of the file before you try and change anything. You could also open an image reader like photoshop or whatever Macs use to read pictures and going to File/Open and then selecting "All Files" and trying to open your file that way.

Sounds confusing, sorry. Hope you can figure it out, brain scans are cool.

This link might help: https://discussions.apple.com/thread/5575331