LIE (also known as MULIE) is a free tool that requires no installation and can be run in the MSDOS setting. Its aim is to solve differential equations from the paramaters you give it.
But LIE also has other commands to get the values of the equations to be solved. Additionally it can be used to find special solutions that are similar to the original, keeping all the quantities.
The LIE user can apply reductions to the distinct differential equation exercises in order to simplify them.