I worked at MS in the Multimedia group working on things like sound-card and CD-ROM drivers, "MMSDK" tools, etc., and the venerable (lol) Radio Shack VIS, which

I worked at MS in the Multimedia group working on things like sound-card and CD-ROM drivers, "MMSDK" tools, etc., and the venerable (lol) Radio Shack VIS, which had a version if Encarta. FWIR, most of the animations used Marcromind Director -- I remember working on the code that loaded these files to optimize it for CD-ROM loading, because the code would just seek all over the place rather than load into RAM and access from there.