The file extension *.bin stands for binary. These files are used extensively in DOS and WIN9X, mostly for running 16-bit software, including some utilities and driver calls. There are also some old DOS utilities with *.bin file exensions.
Some *.bin files contain assembler routines to speed up threads and reduce CPU utilization.
You can open *.bin files with a disk editor, but I can't imagine for what purpose, unless you think reinstalling your OS is a kick.
If you start renaming *.bin file extensions, your going to greatly *INCREASE* your chances of system crashes and hard lockups, especially in WIN9X