There is only one file type that uses the .X86 extension:
Linux Executable File
Executable program file created for the Linux operating system; contains an application in binary format that is run as an executable; similar to the .EXE file in Microsoft Windows.
To enable execution of the X86 file, right-click the file, select, click the "Permissions" tab, and check the "Allow executing file as program" checkbox next to "Execute." If Linux still fails to run the X86 file, it's most likely dynamically linked to libraries, so you will need to install the missing libraries before the X86 file can be run.
Updated: August 30, 2013