and what version of media player should they have to view my MPEG-1 videos
The easy answer for this is that ALL versions of WiMP can handle MPEG-1. The MPEG-1 standard was finished in 1993, which, as you know, predates Windows 95 by a considerable margin.
That being said, anyone who is still using Win 95 is probably suffering deep enough performance issues that you may have other reliability issues with your AMS projects to worry about. Not because the operating system can't handle it, but because the processors those systems likely have are too slow, RAM's a question, hard drive speed is paltry, and CD-ROM drives are SLOW. I/O on such systems will prevent most video files from playing smoothly as well.