Searching for that filename returns some very nostalgic websites. Here's one[0], which refers to speaker.drv as a way to play audio in NCSA Mosaic. It links to SPEAK.EXE on ftp.microsoft.com; incredibly, the URL[1] still works. The page must be about 20 years old.

[0] https://boutell.com/faq/oldfaq/winsound.htm [1] ftp://ftp.microsoft.com/Softlib/MSLFILES/SPEAK.EXE