Macsyma
Macsyma (Project MAC’s SYmbolic MAnipulator) is one the oldest general purpose computer algebra systems which is still widely used. It was originally developed from 1968 to 1982 at MIT's Project MAC.
In 1982, Macsyma was licensed to Symbolics and became a commercial product. In 1992, Symbolics Macsyma was spun off to Macsyma, Inc., which continued to develop Macsyma until 1999. That version is still available for Microsoft's Windows XP operating system.