Do you have a light MathCAD version (not a 1GB download) similar to MathCAD 6 (18MB), but able to run under on Windows 7? Actually I am fully satisfied with MathCAD 6+ but it does not run under Windows 7.
There is a light version called MathCAD Express and it's available for testing through the link posted below. There is also a system requirements PDF file that tells you the operating systems where the software is running perfectly, but Windows 10 doesn't appear to be a supported OS.
Here is the table with the OS list:
Download page: http://www.ptc.com/engineering-math-software/mathcad/free-download