NORMIX is a program for clustering data that consists of a Mixture of multivariate Normal distributions. It was originally developed in the period 1960-1969, but has been adapted to run under MSDOS-Windows9*, while changing the algorithms as little as possible. More information is contained in my papers, three of which can be downloaded in Adobe PDF format. The program itself is freeware that you can download. Even more complete list of papers may be ordered, although many of these are mainly of historical interest.
Since my discovery of the mixture approach to clustering, many others have contributed to the theory, and other programs are available to separate mixtures. Check the sites listed here.