
Some on here seem to be way overcomplicating things. Just stick the movie files on any old box with a large drive (even a Raspberry Pi could work with external USB drives) and then access them via some form of file share: ssh (sftp, sshfs), nfs, cifs, etc. And then play the file with a standard media player, VLC, mpv… most media players are smart enough not to try to load the entire file at once and so streaming is automatic.

Hardware-facing software as well. Usually involving some proprietary super sketchy driver and it might even only work on specific versions of Windows.