3D Pinball Space Cadet was never available for free in a standalone version, no. It originated with the Windows 95 Plus! pack, but that was a commercial product and not a free download. The Windows 98 CD had an INF file that allowed for easy installation from the 95 Plus! CD, but that's as far as it goes.
http://www.mdgx.com/newtip23.htm#3DPI

Pogo.com used to have The Sims Pinball, which is quite obviously derived from 3D Pinball Space Cadet, but that's been retired.
http://www.youtube.com/watch?v=hC5zUo3U5Dw

The commercial version by Maxis was called Full Tilt Pinball. Further details are easily found by searching.