I assume the 32 bit windows wasn't Windows 10 either. Anyway, Mathcad 14 and 15 should be able to run on Windows 10 64 bit. It's a matter of having the right prerequisites. Search a bit on this forum for mathacd 14, 15 and prerequisites and you should find what you need (to install). E.g. here: installation of Mathcad 15 on Windows 10 computer. I should think that you need 32 bit version of MSXML.