Please follow the links and directions to download Microsoft Mathematics. This is Free. A former BSU student Richard Charette brought this to my attention and it is really great.

Note below the really nice feature 'Solution steps' - I did a matrix determinant and simple physics F= ma problems using 'Equation Solver' and then asked it to show me the solution steps.

NOTE: I downloaded the 32-bit setup file for my version of word.

Once you download this, it is stand alone executable, see image below, (make short cult to the Microsoft Mathematics application in program files/Microsoft Mathematics/)

and it can also be embedded into Word, a cool Word Add-In, if you follow the steps to download the set up file to embed into Word.
Here is tutorial of how it works as a Word add-in: Microsoft Mathematics as Word Add-In

From Wiki Microsoft Mathematics