VladimairN. the file was right at the start when clicking install, haven't gone back to look as MartinHanak says the v14 may not run on Windows v8.1.
What I can confirm is that Prime v3 and MathCad v15 do run on a Mac Pro with Parallels v9 but only after a lot of additional Mircosoft Net upgrades, all called up by the installation so sucess.
Old thread this one, but anyway a short note: Any Mathcad will run under any Windows so far. What will not run is the license system, so there is just one thing to do about that: bypass it.
And that is perfectly legal to do in EU. If it is the case anywhere else I have no idea. And in EU you of course need to have a license to Mathcad to run it legally.